diff --git a/codegen/src/function.rs b/codegen/src/function.rs
index 0dba5afa..89358274 100644
--- a/codegen/src/function.rs
+++ b/codegen/src/function.rs
@@ -148,6 +148,16 @@ impl Parse for ExportedFn {
         let entire_span = fn_all.span();
         let str_type_path = syn::parse2::<syn::Path>(quote! { str }).unwrap();
 
+        // #[cfg] attributes are not allowed on functions due to what is generated for them
+        if let Some(cfg_attr) = fn_all.attrs.iter().find(|a| {
+            a.path
+                .get_ident()
+                .map(|i| i.to_string() == "cfg")
+                .unwrap_or(false)
+        }) {
+            return Err(syn::Error::new(cfg_attr.span(), "cfg attributes not allowed on this item"));
+        }
+
         // Determine if the function is public.
         let is_public = match fn_all.vis {
             syn::Visibility::Public(_) => true,
@@ -1057,12 +1067,3 @@ mod generate_tests {
         assert_streams_eq(item_fn.generate(), expected_tokens);
     }
 }
-
-#[cfg(test)]
-mod ui_tests {
-    #[test]
-    fn all() {
-        let t = trybuild::TestCases::new();
-        t.compile_fail("ui_tests/*.rs");
-    }
-}
diff --git a/codegen/src/module.rs b/codegen/src/module.rs
index c6bd6469..34b67876 100644
--- a/codegen/src/module.rs
+++ b/codegen/src/module.rs
@@ -11,11 +11,24 @@ use std::vec as new_vec;
 
 #[cfg(no_std)]
 use core::mem;
+#[cfg(not(no_std))]
+use std::mem;
 
 use std::borrow::Cow;
 use std::collections::HashMap;
 
 fn inner_fn_attributes(f: &mut syn::ItemFn) -> syn::Result<ExportedFnParams> {
+    // #[cfg] attributes are not allowed on objects
+    if let Some(cfg_attr) = f.attrs.iter().find(|a| {
+        a.path
+            .get_ident()
+            .map(|i| i.to_string() == "cfg")
+            .unwrap_or(false)
+    }) {
+        return Err(syn::Error::new(cfg_attr.span(), "cfg attributes not allowed on this item"));
+    }
+
+    // Find the #[rhai_fn] attribute which will turn be read for the function parameters.
     if let Some(rhai_fn_idx) = f.attrs.iter().position(|a| {
         a.path
             .get_ident()
@@ -186,7 +199,7 @@ impl Parse for Module {
     fn parse(input: ParseStream) -> syn::Result<Self> {
         let mut mod_all: syn::ItemMod = input.parse()?;
         let fns: Vec<_>;
-        let consts: Vec<_>;
+        let mut consts: Vec<_> = new_vec![];
         let mut submodules: Vec<_> = Vec::new();
         if let Some((_, ref mut content)) = mod_all.content {
             // Gather and parse functions.
@@ -210,24 +223,33 @@ impl Parse for Module {
                         .map(|_| vec)
                 })?;
             // Gather and parse constants definitions.
-            consts = content
-                .iter()
-                .filter_map(|item| match item {
+            for item in content.iter() {
+                match item {
                     syn::Item::Const(syn::ItemConst {
                         vis,
                         ref expr,
                         ident,
+                        attrs,
                         ..
                     }) => {
-                        if let syn::Visibility::Public(_) = vis {
-                            Some((ident.to_string(), expr.as_ref().clone()))
-                        } else {
-                            None
+                        // #[cfg] attributes are not allowed on const declarations
+                        if let Some(cfg_attr) = attrs.iter().find(|a| {
+                            a.path
+                                .get_ident()
+                                .map(|i| i.to_string() == "cfg")
+                                .unwrap_or(false)
+                        }) {
+                            return Err(syn::Error::new(
+                                    cfg_attr.span(),
+                                    "cfg attributes not allowed on this item"));
                         }
-                    }
-                    _ => None,
-                })
-                .collect();
+                        if let syn::Visibility::Public(_) = vis {
+                            consts.push((ident.to_string(), expr.as_ref().clone()));
+                        }
+                    },
+                    _ => {},
+                }
+            };
             // Gather and parse submodule definitions.
             //
             // They are actually removed from the module's body, because they will need
@@ -257,7 +279,6 @@ impl Parse for Module {
                 }
             }
         } else {
-            consts = new_vec![];
             fns = new_vec![];
         }
         Ok(Module {
@@ -271,6 +292,10 @@ impl Parse for Module {
 }
 
 impl Module {
+    pub fn attrs(&self) -> Option<&Vec<syn::Attribute>> {
+        self.mod_all.as_ref().map(|m| &m.attrs)
+    }
+
     pub fn module_name(&self) -> Option<&syn::Ident> {
         self.mod_all.as_ref().map(|m| &m.ident)
     }
@@ -313,8 +338,10 @@ impl Module {
         let mut mod_all = mod_all.unwrap();
         let mod_name = mod_all.ident.clone();
         let (_, orig_content) = mod_all.content.take().unwrap();
+        let mod_attrs = mem::replace(&mut mod_all.attrs, Vec::with_capacity(0));
 
         Ok(quote! {
+            #(#mod_attrs)*
             pub mod #mod_name {
                 #(#orig_content)*
                 #(#inner_modules)*
@@ -1101,7 +1128,82 @@ mod generate_tests {
                 #[allow(unused_mut)]
                 pub fn rhai_module_generate() -> Module {
                     let mut m = Module::new();
-                    m.set_sub_module("it_is", self::it_is::rhai_module_generate());
+                    { m.set_sub_module("it_is", self::it_is::rhai_module_generate()); }
+                    m
+                }
+            }
+        };
+
+        let item_mod = syn::parse2::<Module>(input_tokens).unwrap();
+        assert_streams_eq(item_mod.generate(), expected_tokens);
+    }
+
+    #[test]
+    fn one_fn_with_cfg_module() {
+        let input_tokens: TokenStream = quote! {
+            pub mod one_fn {
+                #[cfg(not(feature = "no_float"))]
+                pub mod it_is {
+                    pub fn increment(x: &mut FLOAT) {
+                        *x += 1.0 as FLOAT;
+                    }
+                }
+            }
+        };
+
+        let expected_tokens = quote! {
+            pub mod one_fn {
+                #[cfg(not(feature = "no_float"))]
+                pub mod it_is {
+                    pub fn increment(x: &mut FLOAT) {
+                        *x += 1.0 as FLOAT;
+                    }
+                    #[allow(unused_imports)]
+                    use super::*;
+                    #[allow(unused_mut)]
+                    pub fn rhai_module_generate() -> Module {
+                        let mut m = Module::new();
+                        m.set_fn("increment", FnAccess::Public,
+                                 &[core::any::TypeId::of::<FLOAT>()],
+                                 CallableFunction::from_plugin(increment_token()));
+                        m
+                    }
+                    #[allow(non_camel_case_types)]
+                    struct increment_token();
+                    impl PluginFunction for increment_token {
+                        fn call(&self,
+                                args: &mut [&mut Dynamic], pos: Position
+                        ) -> Result<Dynamic, Box<EvalAltResult>> {
+                            debug_assert_eq!(args.len(), 1usize,
+                                                "wrong arg count: {} != {}", args.len(), 1usize);
+                            let arg0: &mut _ = &mut args[0usize].write_lock::<FLOAT>().unwrap();
+                            Ok(Dynamic::from(increment(arg0)))
+                        }
+
+                        fn is_method_call(&self) -> bool { true }
+                        fn is_varadic(&self) -> bool { false }
+                        fn clone_boxed(&self) -> Box<dyn PluginFunction> {
+                            Box::new(increment_token())
+                        }
+                        fn input_types(&self) -> Box<[TypeId]> {
+                            new_vec![TypeId::of::<FLOAT>()].into_boxed_slice()
+                        }
+                    }
+                    pub fn increment_token_callable() -> CallableFunction {
+                        CallableFunction::from_plugin(increment_token())
+                    }
+                    pub fn increment_token_input_types() -> Box<[TypeId]> {
+                        increment_token().input_types()
+                    }
+                }
+                #[allow(unused_imports)]
+                use super::*;
+                #[allow(unused_mut)]
+                pub fn rhai_module_generate() -> Module {
+                    let mut m = Module::new();
+                    #[cfg(not(feature = "no_float"))] {
+                        m.set_sub_module("it_is", self::it_is::rhai_module_generate());
+                    }
                     m
                 }
             }
@@ -1139,7 +1241,7 @@ mod generate_tests {
                 #[allow(unused_mut)]
                 pub fn rhai_module_generate() -> Module {
                     let mut m = Module::new();
-                    m.set_sub_module("it_is", self::it_is::rhai_module_generate());
+                    { m.set_sub_module("it_is", self::it_is::rhai_module_generate()); }
                     m
                 }
             }
@@ -1191,8 +1293,8 @@ mod generate_tests {
                 #[allow(unused_mut)]
                 pub fn rhai_module_generate() -> Module {
                     let mut m = Module::new();
-                    m.set_sub_module("first_is", self::first_is::rhai_module_generate());
-                    m.set_sub_module("second_is", self::second_is::rhai_module_generate());
+                    { m.set_sub_module("first_is", self::first_is::rhai_module_generate()); }
+                    { m.set_sub_module("second_is", self::second_is::rhai_module_generate()); }
                     m
                 }
             }
@@ -1269,8 +1371,8 @@ mod generate_tests {
                         pub fn rhai_module_generate() -> Module {
                             let mut m = Module::new();
                             m.set_var("VALUE", 17);
-                            m.set_sub_module("left", self::left::rhai_module_generate());
-                            m.set_sub_module("right", self::right::rhai_module_generate());
+                            { m.set_sub_module("left", self::left::rhai_module_generate()); }
+                            { m.set_sub_module("right", self::right::rhai_module_generate()); }
                             m
                         }
                     }
@@ -1291,8 +1393,8 @@ mod generate_tests {
                     pub fn rhai_module_generate() -> Module {
                         let mut m = Module::new();
                         m.set_var("VALUE", 19);
-                        m.set_sub_module("left", self::left::rhai_module_generate());
-                        m.set_sub_module("right", self::right::rhai_module_generate());
+                        { m.set_sub_module("left", self::left::rhai_module_generate()); }
+                        { m.set_sub_module("right", self::right::rhai_module_generate()); }
                         m
                     }
                 }
@@ -1326,8 +1428,8 @@ mod generate_tests {
                     pub fn rhai_module_generate() -> Module {
                         let mut m = Module::new();
                         m.set_var("VALUE", 36);
-                        m.set_sub_module("left", self::left::rhai_module_generate());
-                        m.set_sub_module("right", self::right::rhai_module_generate());
+                        { m.set_sub_module("left", self::left::rhai_module_generate()); }
+                        { m.set_sub_module("right", self::right::rhai_module_generate()); }
                         m
                     }
                 }
@@ -1337,8 +1439,8 @@ mod generate_tests {
                 pub fn rhai_module_generate() -> Module {
                     let mut m = Module::new();
                     m.set_var("VALUE", 100);
-                    m.set_sub_module("left", self::left::rhai_module_generate());
-                    m.set_sub_module("right", self::right::rhai_module_generate());
+                    { m.set_sub_module("left", self::left::rhai_module_generate()); }
+                    { m.set_sub_module("right", self::right::rhai_module_generate()); }
                     m
                 }
             }
diff --git a/codegen/src/rhai_module.rs b/codegen/src/rhai_module.rs
index f4f7369e..c327c71f 100644
--- a/codegen/src/rhai_module.rs
+++ b/codegen/src/rhai_module.rs
@@ -12,7 +12,7 @@ pub(crate) fn generate_body(
 ) -> proc_macro2::TokenStream {
     let mut set_fn_stmts: Vec<syn::Stmt> = Vec::new();
     let mut set_const_stmts: Vec<syn::Stmt> = Vec::new();
-    let mut add_mod_stmts: Vec<syn::Stmt> = Vec::new();
+    let mut add_mod_blocks: Vec<syn::ExprBlock> = Vec::new();
     let str_type_path = syn::parse2::<syn::Path>(quote! { str }).unwrap();
 
     for (const_name, const_expr) in consts {
@@ -32,9 +32,16 @@ pub(crate) fn generate_body(
         } else {
             syn::LitStr::new(&module_name.to_string(), proc_macro2::Span::call_site())
         };
-        add_mod_stmts.push(
-            syn::parse2::<syn::Stmt>(quote! {
-                m.set_sub_module(#exported_name, self::#module_name::rhai_module_generate());
+        let cfg_attrs: Vec<&syn::Attribute> = itemmod.attrs().unwrap().iter().filter(|&a| {
+            a.path.get_ident()
+                .map(|i| i.to_string() == "cfg")
+                .unwrap_or(false)
+        }).collect();
+        add_mod_blocks.push(
+            syn::parse2::<syn::ExprBlock>(quote! {
+                #(#cfg_attrs)* {
+                    m.set_sub_module(#exported_name, self::#module_name::rhai_module_generate());
+                }
             })
             .unwrap(),
         );
@@ -117,7 +124,7 @@ pub(crate) fn generate_body(
                 let mut m = Module::new();
                 #(#set_fn_stmts)*
                 #(#set_const_stmts)*
-                #(#add_mod_stmts)*
+                #(#add_mod_blocks)*
                 m
             }
         }
diff --git a/codegen/tests/ui_tests.rs b/codegen/tests/ui_tests.rs
new file mode 100644
index 00000000..ef7bf58f
--- /dev/null
+++ b/codegen/tests/ui_tests.rs
@@ -0,0 +1,8 @@
+#![cfg(test)]
+mod ui_tests {
+    #[test]
+    fn all() {
+        let t = trybuild::TestCases::new();
+        t.compile_fail("ui_tests/*.rs");
+    }
+}
diff --git a/codegen/ui_tests/export_fn_cfg.rs b/codegen/ui_tests/export_fn_cfg.rs
new file mode 100644
index 00000000..52d4c963
--- /dev/null
+++ b/codegen/ui_tests/export_fn_cfg.rs
@@ -0,0 +1,25 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[cfg(not(feature = "foo"))]
+#[export_fn]
+pub fn test_fn(input: Point) -> bool {
+    input.x > input.y
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/export_fn_cfg.stderr b/codegen/ui_tests/export_fn_cfg.stderr
new file mode 100644
index 00000000..ac068be8
--- /dev/null
+++ b/codegen/ui_tests/export_fn_cfg.stderr
@@ -0,0 +1,11 @@
+error: cfg attributes not allowed on this item
+ --> $DIR/export_fn_cfg.rs:9:1
+  |
+9 | #[cfg(not(feature = "foo"))]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0425]: cannot find function `test_fn` in this scope
+  --> $DIR/export_fn_cfg.rs:20:8
+   |
+20 |     if test_fn(n) {
+   |        ^^^^^^^ not found in this scope
diff --git a/codegen/ui_tests/module_cfg_const.rs b/codegen/ui_tests/module_cfg_const.rs
new file mode 100644
index 00000000..599f52da
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_const.rs
@@ -0,0 +1,31 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_module]
+pub mod test_module {
+    use rhai::FLOAT;
+
+    #[cfg(feature = "foo")]
+    pub const MAGIC: FLOAT = 42.0 as FLOAT;
+
+    pub fn test_fn(input: Point) -> bool {
+        input.x > input.y
+    }
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_module::test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/module_cfg_const.stderr b/codegen/ui_tests/module_cfg_const.stderr
new file mode 100644
index 00000000..4eaf1b06
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_const.stderr
@@ -0,0 +1,11 @@
+error: cfg attributes not allowed on this item
+  --> $DIR/module_cfg_const.rs:13:5
+   |
+13 |     #[cfg(feature = "foo")]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0433]: failed to resolve: use of undeclared type or module `test_module`
+  --> $DIR/module_cfg_const.rs:26:8
+   |
+26 |     if test_module::test_fn(n) {
+   |        ^^^^^^^^^^^ use of undeclared type or module `test_module`
diff --git a/codegen/ui_tests/module_cfg_fn.rs b/codegen/ui_tests/module_cfg_fn.rs
new file mode 100644
index 00000000..3613b9a5
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_fn.rs
@@ -0,0 +1,27 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_module]
+pub mod test_module {
+    #[cfg(not(feature = "foo"))]
+    pub fn test_fn(input: Point) -> bool {
+        input.x > input.y
+    }
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_module::test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/module_cfg_fn.stderr b/codegen/ui_tests/module_cfg_fn.stderr
new file mode 100644
index 00000000..80ac12f8
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_fn.stderr
@@ -0,0 +1,11 @@
+error: cfg attributes not allowed on this item
+  --> $DIR/module_cfg_fn.rs:11:5
+   |
+11 |     #[cfg(not(feature = "foo"))]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0433]: failed to resolve: use of undeclared type or module `test_module`
+  --> $DIR/module_cfg_fn.rs:22:8
+   |
+22 |     if test_module::test_fn(n) {
+   |        ^^^^^^^^^^^ use of undeclared type or module `test_module`
diff --git a/codegen/ui_tests/rhai_mod_inner_cfg_false.rs b/codegen/ui_tests/rhai_mod_inner_cfg_false.rs
new file mode 100644
index 00000000..cfb3e1b6
--- /dev/null
+++ b/codegen/ui_tests/rhai_mod_inner_cfg_false.rs
@@ -0,0 +1,29 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_module]
+pub mod test_module {
+    #[cfg(feature = "unset_feature")]
+    pub mod test_mod {
+        pub fn test_fn(input: Point) -> bool {
+            input.x > input.y
+        }
+    }
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_module::test_mod::test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/rhai_mod_inner_cfg_false.stderr b/codegen/ui_tests/rhai_mod_inner_cfg_false.stderr
new file mode 100644
index 00000000..04068220
--- /dev/null
+++ b/codegen/ui_tests/rhai_mod_inner_cfg_false.stderr
@@ -0,0 +1,5 @@
+error[E0433]: failed to resolve: could not find `test_mod` in `test_module`
+  --> $DIR/rhai_mod_inner_cfg_false.rs:24:21
+   |
+24 |     if test_module::test_mod::test_fn(n) {
+   |                     ^^^^^^^^ could not find `test_mod` in `test_module`
diff --git a/src/packages/string_basic.rs b/src/packages/string_basic.rs
index 020f9292..827ba183 100644
--- a/src/packages/string_basic.rs
+++ b/src/packages/string_basic.rs
@@ -88,9 +88,9 @@ def_package!(crate:BasicStringPackage:"Basic string utilities, including printin
 
     #[cfg(not(feature = "no_object"))]
     {
-        set_exported_fn!(lib, KEYWORD_PRINT, format_map);
-        set_exported_fn!(lib, FN_TO_STRING, format_map);
-        set_exported_fn!(lib, KEYWORD_DEBUG, format_map);
+        set_exported_fn!(lib, KEYWORD_PRINT, format_map::format_map);
+        set_exported_fn!(lib, FN_TO_STRING, format_map::format_map);
+        set_exported_fn!(lib, KEYWORD_DEBUG, format_map::format_map);
     }
 });
 
@@ -154,8 +154,11 @@ fn to_debug<T: Debug>(x: &mut T) -> ImmutableString {
     format!("{:?}", x).into()
 }
 #[cfg(not(feature = "no_object"))]
-#[export_fn]
-#[inline]
-fn format_map(x: &mut Map) -> ImmutableString {
-    format!("#{:?}", x).into()
+mod format_map {
+    use super::*;
+    #[inline]
+    #[export_fn]
+    pub fn format_map(x: &mut Map) -> ImmutableString {
+        format!("#{:?}", x).into()
+    }
 }