diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab32c6e4..513329e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ Bug fixes
 ---------
 
 * Invalid property or method access such as `a.b::c.d` or `a.b::func()` no longer panics but properly returns a syntax error.
+* `Scope::is_constant` now returns the correct value.
 
 Enhancements
 ------------
diff --git a/src/types/scope.rs b/src/types/scope.rs
index 7114f8a3..310877c7 100644
--- a/src/types/scope.rs
+++ b/src/types/scope.rs
@@ -375,9 +375,11 @@ impl Scope<'_> {
     /// ```
     #[inline]
     pub fn is_constant(&self, name: &str) -> Option<bool> {
-        self.get_index(name).and_then(|(.., access)| match access {
-            AccessMode::ReadWrite => None,
-            AccessMode::ReadOnly => Some(true),
+        self.get_index(name).and_then(|(.., access)| {
+            Some(match access {
+                AccessMode::ReadWrite => false,
+                AccessMode::ReadOnly => true,
+            })
         })
     }
     /// Update the value of the named entry in the [`Scope`] if it already exists and is not constant.