diff --git a/src/engine.rs b/src/engine.rs
index 84c85701..3520108f 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -304,7 +304,7 @@ impl Engine {
         };
 
         // Add the global namespace module
-        let mut global_namespace = Module::new();
+        let mut global_namespace = Module::with_capacity(0);
         global_namespace.internal = true;
         engine.global_modules.push(global_namespace.into());
 
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 68fbdbbf..bbff05d5 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -270,27 +270,10 @@ impl Module {
     /// module.set_var("answer", 42_i64);
     /// assert_eq!(module.get_var_value::<i64>("answer").expect("answer should exist"), 42);
     /// ```
-    #[inline]
+    #[inline(always)]
     #[must_use]
     pub fn new() -> Self {
-        Self {
-            id: Identifier::new_const(),
-            #[cfg(feature = "metadata")]
-            doc: crate::SmartString::new_const(),
-            internal: false,
-            standard: false,
-            custom_types: None,
-            modules: None,
-            variables: None,
-            all_variables: None,
-            functions: StraightHashMap::default(),
-            all_functions: None,
-            dynamic_functions: BloomFilterU64::new(),
-            type_iterators: None,
-            all_type_iterators: None,
-            indexed: true,
-            contains_indexed_global_functions: false,
-        }
+        Self::with_capacity(16)
     }
     /// Create a new [`Module`] with a pre-sized capacity for functions.
     ///
@@ -486,7 +469,7 @@ impl Module {
     #[inline(always)]
     pub fn set_custom_type<T>(&mut self, name: &str) -> &mut Self {
         self.custom_types
-            .get_or_insert_with(|| Default::default())
+            .get_or_insert_with(CustomTypesCollection::new)
             .add_type::<T>(name);
         self
     }
@@ -512,7 +495,7 @@ impl Module {
         name: impl Into<Identifier>,
     ) -> &mut Self {
         self.custom_types
-            .get_or_insert_with(|| Default::default())
+            .get_or_insert_with(CustomTypesCollection::new)
             .add(type_name, name);
         self
     }
@@ -1752,7 +1735,7 @@ impl Module {
             if let Some(ref mut m) = self.modules {
                 m.extend(modules.iter().map(|(k, v)| (k.clone(), v.clone())));
             } else {
-                m = modules.clone();
+                self.modules = Some(modules.clone());
             }
         }
 
diff --git a/src/packages/lang_core.rs b/src/packages/lang_core.rs
index 25cfaee0..5eaa5ea3 100644
--- a/src/packages/lang_core.rs
+++ b/src/packages/lang_core.rs
@@ -1,7 +1,7 @@
 use crate::def_package;
 use crate::plugin::*;
 use crate::types::dynamic::Tag;
-use crate::{Dynamic, RhaiResultOf, ERR, INT, MAX_USIZE_INT};
+use crate::{Dynamic, RhaiResultOf, ERR, INT};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
@@ -113,7 +113,7 @@ mod reflection_functions {
     }
     #[rhai_fn(name = "get_fn_metadata_list")]
     pub fn get_fn_metadata2(ctx: NativeCallContext, name: &str, params: INT) -> crate::Array {
-        if params < 0 || params > MAX_USIZE_INT {
+        if params < 0 || params > crate::MAX_USIZE_INT {
             crate::Array::new()
         } else {
             collect_fn_metadata(ctx, |_, _, n, p, _| p == (params as usize) && n == name)
diff --git a/src/types/custom_types.rs b/src/types/custom_types.rs
index b0cb8bfd..3b759edc 100644
--- a/src/types/custom_types.rs
+++ b/src/types/custom_types.rs
@@ -29,11 +29,6 @@ impl CustomTypesCollection {
     pub fn new() -> Self {
         Self(BTreeMap::new())
     }
-    /// Clear the [`CustomTypesCollection`].
-    #[inline(always)]
-    pub fn clear(&mut self) {
-        self.0.clear();
-    }
     /// Register a custom type.
     #[inline(always)]
     pub fn add(&mut self, type_name: impl Into<Identifier>, name: impl Into<Identifier>) {