diff --git a/core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java b/core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java
index 30a5a3da9..1e93c731b 100644
--- a/core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java
+++ b/core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java
@@ -134,7 +134,7 @@ public class WasmGCClassGenerator implements WasmGCClassInfoProvider, WasmGCInit
     private int classNameOffset;
     private int classSimpleNameOffset;
     private int classCanonicalNameOffset;
-    private int classParentOffset;
+    private int classParentOffset = -1;
     private int classArrayOffset;
     private int classArrayItemOffset;
     private int classNewArrayOffset;
@@ -1438,12 +1438,14 @@ public class WasmGCClassGenerator implements WasmGCClassInfoProvider, WasmGCInit
                 classTagOffset,
                 new WasmInt32Constant(0)
         ));
-        function.getBody().add(new WasmStructSet(
-                standardClasses.classClass().getStructure(),
-                new WasmGetLocal(targetVar),
-                classParentOffset,
-                new WasmGetGlobal(standardClasses.objectClass().pointer)
-        ));
+        if (classParentOffset >= 0) {
+            function.getBody().add(new WasmStructSet(
+                    standardClasses.classClass().getStructure(),
+                    new WasmGetLocal(targetVar),
+                    classParentOffset,
+                    new WasmGetGlobal(standardClasses.objectClass().pointer)
+            ));
+        }
         return function;
     }
 
diff --git a/core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationVisitor.java b/core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationVisitor.java
index e38951336..a89594ce0 100644
--- a/core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationVisitor.java
+++ b/core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationVisitor.java
@@ -480,9 +480,10 @@ public class WasmGCGenerationVisitor extends BaseWasmGenerationVisitor {
                 canInsertCast = false;
             } else if (!sourceStruct.isSupertypeOf(targetStruct)) {
                 var block = new WasmBlock(false);
+                block.setType(targetType);
                 block.setLocation(expr.getLocation());
-                block.getBody().add(result);
-                block.getBody().add(new WasmUnreachable());
+                block.getBody().add(new WasmDrop(result));
+                block.getBody().add(new WasmNullConstant(targetType));
                 result = block;
                 return;
             }
diff --git a/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/CompositeMethodGenerator.java b/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/CompositeMethodGenerator.java
index 973774afc..880e67fda 100644
--- a/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/CompositeMethodGenerator.java
+++ b/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/CompositeMethodGenerator.java
@@ -878,7 +878,15 @@ public class CompositeMethodGenerator {
                 case "get": {
                     Variable var = program.createVariable();
                     GetFieldInstruction insn = new GetFieldInstruction();
-                    insn.setInstance(!field.field.hasModifier(ElementModifier.STATIC) ? var(arguments.get(0)) : null);
+                    if (!field.field.hasModifier(ElementModifier.STATIC)) {
+                        var cast = new CastInstruction();
+                        cast.setReceiver(program.createVariable());
+                        cast.setValue(var(arguments.get(0)));
+                        cast.setWeak(true);
+                        cast.setTargetType(ValueType.object(field.field.getOwnerName()));
+                        add(cast);
+                        insn.setInstance(cast.getReceiver());
+                    }
                     insn.setReceiver(var);
                     insn.setField(field.getBackingField().getReference());
                     insn.setFieldType(field.getBackingField().getType());
@@ -895,7 +903,15 @@ public class CompositeMethodGenerator {
                 }
                 case "set": {
                     PutFieldInstruction insn = new PutFieldInstruction();
-                    insn.setInstance(!field.field.hasModifier(ElementModifier.STATIC) ? var(arguments.get(0)) : null);
+                    if (!field.field.hasModifier(ElementModifier.STATIC)) {
+                        var cast = new CastInstruction();
+                        cast.setReceiver(program.createVariable());
+                        cast.setValue(var(arguments.get(0)));
+                        cast.setWeak(true);
+                        cast.setTargetType(ValueType.object(field.field.getOwnerName()));
+                        add(cast);
+                        insn.setInstance(cast.getReceiver());
+                    }
                     insn.setValue(unbox(var(arguments.get(1)), field.getBackingField().getType()));
                     insn.setField(field.getBackingField().getReference());
                     insn.setFieldType(field.getBackingField().getType());
@@ -930,7 +946,15 @@ public class CompositeMethodGenerator {
             switch (method.getName()) {
                 case "invoke": {
                     InvokeInstruction insn = new InvokeInstruction();
-                    insn.setInstance(!Modifier.isStatic(reflectMethod.getModifiers()) ? var(arguments.get(0)) : null);
+                    if (!Modifier.isStatic(reflectMethod.getModifiers())) {
+                        var cast = new CastInstruction();
+                        cast.setReceiver(program.createVariable());
+                        cast.setValue(var(arguments.get(0)));
+                        cast.setWeak(true);
+                        cast.setTargetType(ValueType.object(reflectMethod.method.getOwnerName()));
+                        add(cast);
+                        insn.setInstance(cast.getReceiver());
+                    }
                     insn.setType(Modifier.isStatic(reflectMethod.getModifiers()) ? InvocationType.SPECIAL
                             : InvocationType.VIRTUAL);
                     insn.setMethod(reflectMethod.method.getReference());