diff --git a/teavm-core/src/main/java/org/teavm/javascript/JavascriptBuilder.java b/teavm-core/src/main/java/org/teavm/javascript/JavascriptBuilder.java
index f66b9db8b..dd5046ec4 100644
--- a/teavm-core/src/main/java/org/teavm/javascript/JavascriptBuilder.java
+++ b/teavm-core/src/main/java/org/teavm/javascript/JavascriptBuilder.java
@@ -158,8 +158,8 @@ public class JavascriptBuilder implements JavascriptBuilderHost {
         Linker linker = new Linker(dependencyChecker);
         ListableClassHolderSource classSet = linker.link(classSource);
         Decompiler decompiler = new Decompiler(classSet, classLoader, executor);
-        /*devirtualize(classSet, dependencyChecker);
-        executor.complete();*/
+        devirtualize(classSet, dependencyChecker);
+        executor.complete();
         ClassSetOptimizer optimizer = new ClassSetOptimizer(executor);
         optimizer.optimizeAll(classSet);
         executor.complete();
@@ -199,7 +199,6 @@ public class JavascriptBuilder implements JavascriptBuilderHost {
     }
 
     // TODO: repair devirtualization
-    @SuppressWarnings("unused")
     private void devirtualize(ListableClassHolderSource classes, DependencyInfo dependency) {
         final Devirtualization devirtualization = new Devirtualization(dependency, classes);
         for (String className : classes.getClassNames()) {
diff --git a/teavm-core/src/main/java/org/teavm/optimization/Devirtualization.java b/teavm-core/src/main/java/org/teavm/optimization/Devirtualization.java
index 69f9182cb..4bec24cfa 100644
--- a/teavm-core/src/main/java/org/teavm/optimization/Devirtualization.java
+++ b/teavm-core/src/main/java/org/teavm/optimization/Devirtualization.java
@@ -55,7 +55,7 @@ public class Devirtualization {
                 }
                 ValueDependencyInfo var = methodDep.getVariable(invoke.getInstance().getIndex());
                 Set<MethodReference> implementations = getImplementations(var.getTypes(),
-                        invoke.getMethod().getDescriptor());
+                        invoke.getMethod());
                 if (implementations.size() == 1) {
                     invoke.setType(InvocationType.SPECIAL);
                     invoke.setMethod(implementations.iterator().next());
@@ -64,14 +64,37 @@ public class Devirtualization {
         }
     }
 
-    private Set<MethodReference> getImplementations(String[] classNames, MethodDescriptor desc) {
+    private Set<MethodReference> getImplementations(String[] classNames, MethodReference ref) {
         Set<MethodReference> methods = new HashSet<>();
         for (String className : classNames) {
             ClassReader cls = classSource.get(className);
-            if (cls != null && cls.getMethod(desc) != null) {
-                methods.add(new MethodReference(className, desc));
+            if (cls == null || !isAssignable(ref.getClassName(), cls)) {
+                break;
+            }
+            MethodDependencyInfo methodDep = dependency.getMethod(new MethodReference(className, ref.getDescriptor()));
+            if (methodDep != null) {
+                methods.add(methodDep.getReference());
             }
         }
         return methods;
     }
+
+    private boolean isAssignable(String target, ClassReader cls) {
+        if (cls.getName().equals(target)) {
+            return true;
+        }
+        if (cls.getParent() != null) {
+            ClassReader parent = classSource.get(cls.getParent());
+            if (parent != null && isAssignable(target, parent)) {
+                return true;
+            }
+        }
+        for (String ifaceName : cls.getInterfaces()) {
+            ClassReader iface = classSource.get(ifaceName);
+            if (iface != null && isAssignable(target, iface)) {
+                return true;
+            }
+        }
+        return false;
+    }
 }
diff --git a/teavm-html4j/pom.xml b/teavm-html4j/pom.xml
index 0e6ff5096..3990ca7bc 100644
--- a/teavm-html4j/pom.xml
+++ b/teavm-html4j/pom.xml
@@ -85,7 +85,7 @@
             </goals>
             <phase>process-test-classes</phase>
             <configuration>
-              <minifying>true</minifying>
+              <minifying>false</minifying>
               <numThreads>1</numThreads>
               <scanDependencies>true</scanDependencies>
               <outputDir>${project.build.directory}/javascript-tck</outputDir>