diff --git a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
index ba0b970a0..472e104f9 100644
--- a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
+++ b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
@@ -104,18 +104,20 @@ class JSClassProcessor {
     private final JSTypeHelper typeHelper;
     private final Diagnostics diagnostics;
     private final Map<MethodReference, MethodReader> overriddenMethodCache = new HashMap<>();
+    private final boolean strict;
     private JSValueMarshaller marshaller;
     private IncrementalDependencyRegistration incrementalCache;
     private JSImportAnnotationCache annotationCache;
     private ClassReader objectClass;
 
     JSClassProcessor(ClassReaderSource classSource, JSTypeHelper typeHelper, JSBodyRepository repository,
-            Diagnostics diagnostics, IncrementalDependencyRegistration incrementalCache) {
+            Diagnostics diagnostics, IncrementalDependencyRegistration incrementalCache, boolean strict) {
         this.classSource = classSource;
         this.typeHelper = typeHelper;
         this.repository = repository;
         this.diagnostics = diagnostics;
         this.incrementalCache = incrementalCache;
+        this.strict = strict;
         javaInvocationProcessor = new JavaInvocationProcessor(typeHelper, repository, classSource, diagnostics);
 
         annotationCache = new JSImportAnnotationCache(classSource, diagnostics);
@@ -477,7 +479,7 @@ class JSClassProcessor {
 
         ClassReader targetClass = classSource.get(targetClassName);
         if (targetClass.getAnnotations().get(JSFunctor.class.getName()) == null) {
-            if (isTransparent(targetClassName)) {
+            if (!strict || isTransparent(targetClassName)) {
                 var assign = new AssignInstruction();
                 assign.setLocation(location.getSourceLocation());
                 assign.setAssignee(cast.getValue());
diff --git a/jso/impl/src/main/java/org/teavm/jso/impl/JSObjectClassTransformer.java b/jso/impl/src/main/java/org/teavm/jso/impl/JSObjectClassTransformer.java
index 3137a7ba0..cc4d8a398 100644
--- a/jso/impl/src/main/java/org/teavm/jso/impl/JSObjectClassTransformer.java
+++ b/jso/impl/src/main/java/org/teavm/jso/impl/JSObjectClassTransformer.java
@@ -70,7 +70,7 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
         if (processor == null || processor.getClassSource() != hierarchy.getClassSource()) {
             typeHelper = new JSTypeHelper(hierarchy.getClassSource());
             processor = new JSClassProcessor(hierarchy.getClassSource(), typeHelper, repository,
-                    context.getDiagnostics(), context.getIncrementalCache());
+                    context.getDiagnostics(), context.getIncrementalCache(), context.isStrict());
         }
         processor.processClass(cls);
         if (typeHelper.isJavaScriptClass(cls.getName())) {
diff --git a/tools/junit/src/main/java/org/teavm/junit/TestPlatformSupport.java b/tools/junit/src/main/java/org/teavm/junit/TestPlatformSupport.java
index b6cc01e95..62383bc82 100644
--- a/tools/junit/src/main/java/org/teavm/junit/TestPlatformSupport.java
+++ b/tools/junit/src/main/java/org/teavm/junit/TestPlatformSupport.java
@@ -85,6 +85,7 @@ abstract class TestPlatformSupport<T extends TeaVMTarget> {
                     .setClassSource(classSource)
                     .setReferenceCache(referenceCache)
                     .setDependencyAnalyzerFactory(dependencyAnalyzerFactory)
+                    .setStrict(true)
                     .build();
 
             configuration.apply(vm);