diff --git a/teavm-classlib/src/test/java/org/teavm/platform/metadata/MetadataGeneratorTest.java b/teavm-classlib/src/test/java/org/teavm/platform/metadata/MetadataGeneratorTest.java
index ad4bf808a..ec59b1299 100644
--- a/teavm-classlib/src/test/java/org/teavm/platform/metadata/MetadataGeneratorTest.java
+++ b/teavm-classlib/src/test/java/org/teavm/platform/metadata/MetadataGeneratorTest.java
@@ -61,5 +61,44 @@ public class MetadataGeneratorTest {
         assertEquals("baz", res.getArrayB().get(0).getBar());
         assertNull(res.getArrayC());
     }
+
+    @MetadataProvider(TestResourceGenerator.class)
+    private native TestResource getEmptyResource();
+
+    @Test
+    public void resourceDefaultsSet() {
+        TestResource res = getEmptyResource();
+        assertEquals(0, res.getA());
+        assertFalse(res.getB());
+        assertEquals(0, res.getD());
+        assertEquals(0, res.getE());
+        assertEquals(0, res.getF(), 1E-10);
+        assertEquals(0, res.getG(), 1E-10);
+        assertNull(res.getFoo());
+        assertNull(res.getArrayA());
+        assertNull(res.getArrayB());
+        assertNull(res.getArrayC());
+        assertNull(res.getMapA());
+        assertNull(res.getMapB());
+        assertNull(res.getMapC());
+    }
+
+    @Test
+    public void resourceModifiedInRunTime() {
+        TestResource res = getEmptyResource();
+        res.setA(23);
+        res.setB(true);
+        res.setD((byte)24);
+        res.setE((short)25);
+        res.setF(3.14f);
+        res.setG(2.72);
+
+        assertEquals(23, res.getA());
+        assertTrue(res.getB());
+        assertEquals(24, res.getD());
+        assertEquals(25, res.getE());
+        assertEquals(3.14, res.getF(), 0.001);
+        assertEquals(2.72, res.getG(), 0.001);
+    }
 }
 
diff --git a/teavm-classlib/src/test/java/org/teavm/platform/metadata/TestResourceGenerator.java b/teavm-classlib/src/test/java/org/teavm/platform/metadata/TestResourceGenerator.java
index 6edf353ce..43f672805 100644
--- a/teavm-classlib/src/test/java/org/teavm/platform/metadata/TestResourceGenerator.java
+++ b/teavm-classlib/src/test/java/org/teavm/platform/metadata/TestResourceGenerator.java
@@ -31,6 +31,8 @@ public class TestResourceGenerator implements MetadataGenerator {
                 return createInt(context, 23);
             case "getResource":
                 return getResource(context);
+            case "getEmptyResource":
+                return context.createResource(TestResource.class);
             default:
                 throw new RuntimeException("Unsupported method: " + method);
         }
diff --git a/teavm-platform/src/main/java/org/teavm/platform/plugin/BuildTimeResourceProxyBuilder.java b/teavm-platform/src/main/java/org/teavm/platform/plugin/BuildTimeResourceProxyBuilder.java
index 9e962512a..a936fee0f 100644
--- a/teavm-platform/src/main/java/org/teavm/platform/plugin/BuildTimeResourceProxyBuilder.java
+++ b/teavm-platform/src/main/java/org/teavm/platform/plugin/BuildTimeResourceProxyBuilder.java
@@ -62,6 +62,7 @@ class BuildTimeResourceProxyBuilder {
         Map<Method, BuildTimeResourceMethod> methods = new HashMap<>();
         private Map<String, Integer> propertyIndexes = new HashMap<>();
         private Object[] initialData;
+        private Map<String, Class<?>> propertyTypes = new HashMap<>();
 
         public ProxyFactoryCreation(Class<?> iface) {
             this.rootIface = iface;
@@ -73,12 +74,24 @@ class BuildTimeResourceProxyBuilder {
                         " that is not an interface");
             }
             scanIface(rootIface);
+
+            // Fill default values
+            initialData = new Object[propertyIndexes.size()];
+            for (Map.Entry<String, Class<?>> property : propertyTypes.entrySet()) {
+                String propertyName = property.getKey();
+                Class<?> propertyType = property.getValue();
+                initialData[propertyIndexes.get(propertyName)] = defaultValues.get(propertyType);
+            }
+
+            // Generate write method
             Method writeMethod;
             try {
                 writeMethod = ResourceWriter.class.getMethod("write", SourceWriter.class);
             } catch (NoSuchMethodException e) {
                 throw new AssertionError("Method must exist", e);
             }
+
+            // Create factory
             String[] properties = new String[propertyIndexes.size()];
             for (Map.Entry<String, Integer> entry : propertyIndexes.entrySet()) {
                 properties[entry.getValue()] = entry.getKey();
@@ -129,18 +142,19 @@ class BuildTimeResourceProxyBuilder {
                 }
             }
 
-            // Verify types of properties and fill default values
-            initialData = new Object[propertyIndexes.size()];
+            // Verify types of properties
             for (Map.Entry<String, Class<?>> property : getters.entrySet()) {
                 String propertyName = property.getKey();
                 Class<?> propertyType = property.getValue();
                 if (!allowedPropertyTypes.contains(propertyType)) {
                     if (!propertyType.isInterface() || !Resource.class.isAssignableFrom(propertyType)) {
-                        throw new IllegalArgumentException("Property " + iface.getName() + "." + propertyName +
+                        throw new IllegalArgumentException("Property " + rootIface.getName() + "." + propertyName +
                                 " has an illegal type " + propertyType.getName());
                     }
                 }
-                initialData[propertyIndexes.get(propertyName)] = defaultValues.get(propertyType);
+                if (!propertyTypes.containsKey(propertyName)) {
+                    propertyTypes.put(propertyName, propertyType);
+                }
             }
 
             // Scan superinterfaces
diff --git a/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceAccessorGenerator.java b/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceAccessorGenerator.java
index 73e142c5c..1eaa46a52 100644
--- a/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceAccessorGenerator.java
+++ b/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceAccessorGenerator.java
@@ -52,7 +52,7 @@ class ResourceAccessorGenerator implements Injector {
                     context.writeExpr(context.getArgument(0));
                     writePropertyAccessor(context, context.getArgument(1));
                 }
-                context.getWriter().append(']').ws().append('=').ws();
+                context.getWriter().ws().append('=').ws();
                 context.writeExpr(context.getArgument(2));
                 context.getWriter().append(')');
                 break;
@@ -87,14 +87,20 @@ class ResourceAccessorGenerator implements Injector {
                 context.writeExpr(context.getArgument(0));
                 break;
             case "castToString":
+                context.getWriter().append('(');
+                context.writeExpr(context.getArgument(0));
+                context.getWriter().ws().append("!==").ws().append("null").ws().append("?").ws();
                 context.getWriter().append("$rt_str(");
                 context.writeExpr(context.getArgument(0));
-                context.getWriter().append(")");
+                context.getWriter().append(")").ws().append(':').ws().append("null)");
                 break;
             case "castFromString":
+                context.getWriter().append('(');
+                context.writeExpr(context.getArgument(0));
+                context.getWriter().ws().append("!==").ws().append("null").ws().append("?").ws();
                 context.getWriter().append("$rt_ustr(");
                 context.writeExpr(context.getArgument(0));
-                context.getWriter().append(")");
+                context.getWriter().append(")").ws().append(':').ws().append("null)");
                 break;
         }
     }
diff --git a/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceProgramTransformer.java b/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceProgramTransformer.java
index 798031e2a..56e51343b 100644
--- a/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceProgramTransformer.java
+++ b/teavm-platform/src/main/java/org/teavm/platform/plugin/ResourceProgramTransformer.java
@@ -191,9 +191,88 @@ class ResourceProgramTransformer {
     }
 
     private List<Instruction> transformSetterInvocation(InvokeInstruction insn, String property) {
+        ValueType type = insn.getMethod().getDescriptor().parameterType(0);
+        List<Instruction> instructions = new ArrayList<>();
+        if (type instanceof ValueType.Primitive) {
+            switch (((ValueType.Primitive)type).getKind()) {
+                case BOOLEAN:
+                    castAndSetProperty(insn, property, instructions, boolean.class);
+                    return instructions;
+                case BYTE:
+                    castAndSetProperty(insn, property, instructions, byte.class);
+                    return instructions;
+                case SHORT:
+                    castAndSetProperty(insn, property, instructions, short.class);
+                    return instructions;
+                case INTEGER:
+                    castAndSetProperty(insn, property, instructions, int.class);
+                    return instructions;
+                case FLOAT:
+                    castAndSetProperty(insn, property, instructions, float.class);
+                    return instructions;
+                case DOUBLE:
+                    castAndSetProperty(insn, property, instructions, double.class);
+                    return instructions;
+                case CHARACTER:
+                case LONG:
+                    break;
+            }
+        } else if (type instanceof ValueType.Object) {
+            switch (((ValueType.Object)type).getClassName()) {
+                case "java.lang.String": {
+                    Variable castVar = insn.getProgram().createVariable();
+                    InvokeInstruction castInvoke = new InvokeInstruction();
+                    castInvoke.setType(InvocationType.SPECIAL);
+                    castInvoke.setMethod(new MethodReference(ResourceAccessor.class, "castFromString",
+                            String.class, Object.class));
+                    castInvoke.getArguments().add(insn.getArguments().get(0));
+                    castInvoke.setReceiver(castVar);
+                    instructions.add(castInvoke);
+                    setProperty(insn, property, instructions, castVar);
+                    return instructions;
+                }
+                default: {
+                    setProperty(insn, property, instructions, insn.getArguments().get(0));
+                    return instructions;
+                }
+            }
+        }
         return null;
     }
 
+    private void setProperty(InvokeInstruction insn, String property, List<Instruction> instructions,
+            Variable valueVar) {
+        Variable nameVar = program.createVariable();
+        StringConstantInstruction nameInsn = new StringConstantInstruction();
+        nameInsn.setConstant(property);
+        nameInsn.setReceiver(nameVar);
+        instructions.add(nameInsn);
+        InvokeInstruction accessorInvoke = new InvokeInstruction();
+        accessorInvoke.setType(InvocationType.SPECIAL);
+        accessorInvoke.setMethod(new MethodReference(ResourceAccessor.class, "put",
+                Object.class, String.class, Object.class, void.class));
+        accessorInvoke.getArguments().add(insn.getInstance());
+        accessorInvoke.getArguments().add(nameVar);
+        accessorInvoke.getArguments().add(valueVar);
+        instructions.add(accessorInvoke);
+    }
+
+    private void castAndSetProperty(InvokeInstruction insn, String property, List<Instruction> instructions,
+            Class<?> primitive) {
+        Variable castVar = program.createVariable();
+        InvokeInstruction castInvoke = new InvokeInstruction();
+        castInvoke.setType(InvocationType.SPECIAL);
+        String primitiveCapitalized = primitive.getName();
+        primitiveCapitalized = Character.toUpperCase(primitiveCapitalized.charAt(0)) +
+                primitiveCapitalized.substring(1);
+        castInvoke.setMethod(new MethodReference(ResourceAccessor.class, "castFrom" + primitiveCapitalized,
+                primitive, Object.class));
+        castInvoke.getArguments().add(insn.getArguments().get(0));
+        castInvoke.setReceiver(castVar);
+        instructions.add(castInvoke);
+        setProperty(insn, property, instructions, castVar);
+    }
+
     private String getPropertyName(String name) {
         if (name.length() == 1) {
             return name.toLowerCase();