diff --git a/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java b/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java
index 5e1feec2f..fe72b3a69 100644
--- a/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java
+++ b/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java
@@ -28,6 +28,7 @@ import org.teavm.callgraph.CallGraphNode;
 import org.teavm.callgraph.CallSite;
 import org.teavm.diagnostics.Diagnostics;
 import org.teavm.interop.Async;
+import org.teavm.interop.SuppressSyncErrors;
 import org.teavm.interop.Sync;
 import org.teavm.model.CallLocation;
 import org.teavm.model.ClassReader;
@@ -156,9 +157,17 @@ public class AsyncMethodFinder {
         }
         if (method.getAnnotations().get(Sync.class.getName()) != null
                 || method.getAnnotations().get(InjectedBy.class.getName()) != null) {
-            diagnostics.error(new CallLocation(methodRef), "Method {{m0}} is claimed to be synchronous, "
-                    + "but it is has invocations of asynchronous methods:" + stack.toString(), methodRef);
-            return;
+            if (method.getAnnotations().get(SuppressSyncErrors.class.getName()) == null) {
+                diagnostics.error(new CallLocation(methodRef), "Method {{m0}} is claimed to be "
+                        + "synchronous, but it is has invocations of asynchronous methods:" 
+                        + stack.toString(), methodRef);
+                return;
+            } else {
+                diagnostics.warning(new CallLocation(methodRef), "Error as Warning because "
+                        + " Method {{m0}} has @SuppressSyncErrors annoation. Method {{m0}} "
+                        + "is claimed to be synchronous, but it is has invocations of "
+                        + "asynchronous methods:" + stack.toString(), methodRef);
+            }
         }
         for (CallSite callSite : node.getCallerCallSites()) {
             MethodReference nextMethod = callSite.getCaller().getMethod();
diff --git a/interop/core/src/main/java/org/teavm/interop/SuppressSyncErrors.java b/interop/core/src/main/java/org/teavm/interop/SuppressSyncErrors.java
new file mode 100644
index 000000000..c20bf710a
--- /dev/null
+++ b/interop/core/src/main/java/org/teavm/interop/SuppressSyncErrors.java
@@ -0,0 +1,28 @@
+/*
+ *  Copyright 2016 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.interop;
+
+import java.lang.annotation.*;
+
+/**
+ * 
+ * @author Steve Hannah
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface SuppressSyncErrors {
+}
+