diff --git a/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java b/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
index 9ebbb3aac..8dff00b42 100644
--- a/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
+++ b/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
@@ -663,7 +663,7 @@ public class ClassGenerator {
             itemTypeExpr = "NULL";
         } else {
             parent = "NULL";
-            tag = 0;
+            tag = Integer.MAX_VALUE;
             sizeExpr = "sizeof(" + CodeWriter.strictTypeAsString(type) + ")";
             flags |= RuntimeClass.PRIMITIVE;
             flags = ClassGeneratorUtil.applyPrimitiveFlags(flags, type);
diff --git a/tests/src/test/java/org/teavm/vm/RttiTest.java b/tests/src/test/java/org/teavm/vm/RttiTest.java
index d020574af..bef2241b7 100644
--- a/tests/src/test/java/org/teavm/vm/RttiTest.java
+++ b/tests/src/test/java/org/teavm/vm/RttiTest.java
@@ -15,7 +15,11 @@
  */
 package org.teavm.vm;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import java.util.ArrayList;
+import java.util.List;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.teavm.junit.TeaVMTestRunner;
@@ -33,6 +37,25 @@ public class RttiTest {
         checkImplements(new G(), true, true, false);
     }
 
+    @Test
+    public void objectIsNotSupertypeOfPrimitive() {
+        assertFalse(Object.class.isAssignableFrom(int.class));
+    }
+
+    @Test
+    public void instanceOfObjectArray() {
+        List<Object> list = new ArrayList<>();
+        list.add("123");
+        list.add(new Object[0]);
+        list.add(new String[0]);
+        list.add(new int[0]);
+        StringBuilder sb = new StringBuilder();
+        for (Object item : list) {
+            sb.append(item instanceof Object[] ? 't' : 'f');
+        }
+        assertEquals("fttf", sb.toString());
+    }
+
     private void checkImplements(Object o, boolean i, boolean j, boolean k) {
         assertTrue(predicate(o, i, "I"), !i ^ o instanceof I);
         assertTrue(predicate(o, j, "J"), !j ^ o instanceof J);