diff --git a/Editor/ConditionalCompilationUtility.cs b/Editor/ConditionalCompilationUtility.cs
index a763cfb..2f81030 100644
--- a/Editor/ConditionalCompilationUtility.cs
+++ b/Editor/ConditionalCompilationUtility.cs
@@ -186,6 +186,13 @@ static void UpdateDependencies(bool reset = false)
                 }
             });
 
+            // Remove scripting symbols for optional dependencies that have been removed.
+            foreach (var define in dependencies.Values)
+            {
+                if (projectDefines.Contains(define) && !ccuDefines.Contains(define))
+                    projectDefines.Remove(define);
+            }
+
             if (reset)
             {
                 foreach (var define in dependencies.Values)