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 6ba1a3027..17578f62e 100644
--- a/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java
+++ b/core/src/main/java/org/teavm/model/util/AsyncMethodFinder.java
@@ -72,18 +72,8 @@ public class AsyncMethodFinder {
                     if (asyncMethods.contains(method.getReference()) || method.getProgram() == null) {
                         continue;
                     }
-                    if (method.hasModifier(ElementModifier.SYNCHRONIZED)) {
+                    if (hasMonitor(method)) {
                         add(method.getReference());
-                        continue;
-                    }
-                    ProgramReader program = method.getProgram();
-                    AsyncInstructionReader insnReader = new AsyncInstructionReader();
-                    for (int i = 0; i < program.basicBlockCount(); ++i) {
-                        program.basicBlockAt(i).readAllInstructions(insnReader);
-                        if (insnReader.async) {
-                            add(method.getReference());
-                            break;
-                        }
                     }
                 }
             }
@@ -105,21 +95,36 @@ public class AsyncMethodFinder {
     }
 
     private boolean hasAsyncMethods() {
-        int count = asyncMethods.size();
-        if (asyncMethods.contains(new MethodReference(Object.class, "monitorEnter", Object.class, void.class))) {
-            --count;
-        }
-        if (asyncMethods.contains(new MethodReference(Object.class, "monitorEnter", Object.class,
-                int.class, void.class))) {
-            --count;
-        }
-        if (asyncMethods.contains(new MethodReference(Object.class, "monitorEnterWait", Object.class,
-                int.class, void.class))) {
-            --count;
+        boolean result = false;
+        loop: for (String clsName : classSource.getClassNames()) {
+            ClassReader cls = classSource.get(clsName);
+            for (MethodReader method : cls.getMethods()) {
+                if (!asyncMethods.contains(method.getReference()) || method.getProgram() == null) {
+                    continue;
+                }
+                if (hasMonitor(method)) {
+                    break loop;
+                }
+            }
         }
         ClassReader cls = classSource.get("java.lang.Thread");
         MethodReader method = cls != null ? cls.getMethod(new MethodDescriptor("start", void.class)) : null;
-        return count > 0 && method != null;
+        return result && method != null;
+    }
+
+    private boolean hasMonitor(MethodReader method) {
+        if (method.hasModifier(ElementModifier.SYNCHRONIZED)) {
+            return true;
+        }
+        ProgramReader program = method.getProgram();
+        AsyncInstructionReader insnReader = new AsyncInstructionReader();
+        for (int i = 0; i < program.basicBlockCount(); ++i) {
+            program.basicBlockAt(i).readAllInstructions(insnReader);
+            if (insnReader.async) {
+                return true;
+            }
+        }
+        return false;
     }
 
     private void add(MethodReference methodRef) {
diff --git a/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java b/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
index d3d462bda..d6efb07c7 100644
--- a/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
+++ b/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
@@ -138,7 +138,7 @@ public class JavaScriptConvGenerator implements Generator {
         writer.outdent().append("} else if (" + type + " === ").appendClass("java.lang.Character")
                 .append(") {").indent().softNewLine();
         writer.append("return ").appendMethodBody(valueOfCharMethod).append("(typeof " + obj + " === 'number' ? "
-                + obj + "0xFFFF : " + obj + ".charCodeAt(0));").softNewLine();
+                + obj + " & 0xFFFF : " + obj + ".charCodeAt(0));").softNewLine();
 
         writer.outdent().append("} else if (" + type + " === ").appendClass("java.lang.Byte")
                 .append(") {").indent().softNewLine();
@@ -186,7 +186,7 @@ public class JavaScriptConvGenerator implements Generator {
         writer.append("return $rt_str(" + obj + ");").softNewLine();
 
         writer.outdent().append("} else if (typeof " + obj + " === 'number') {").indent().softNewLine();
-        writer.append("if (" + obj + "|0 === " + obj + ") {").indent().softNewLine();
+        writer.append("if ((" + obj + "|0) === " + obj + ") {").indent().softNewLine();
         writer.append("return ").appendMethodBody(valueOfIntMethod).append("(" + obj + ");").softNewLine();
         writer.outdent().append("} else {").indent().softNewLine();
         writer.append("return ").appendMethodBody(valueOfDoubleMethod).append("(" + obj + ");").softNewLine();
diff --git a/jso/apis/src/main/java/org/teavm/jso/browser/Window.java b/jso/apis/src/main/java/org/teavm/jso/browser/Window.java
index 1309721f9..95c0ac276 100644
--- a/jso/apis/src/main/java/org/teavm/jso/browser/Window.java
+++ b/jso/apis/src/main/java/org/teavm/jso/browser/Window.java
@@ -93,7 +93,7 @@ public abstract class Window implements JSObject, WindowEventTarget, StorageProv
         return prompt(message, "");
     }
 
-    @JSBody(params = { "message", "default" }, script = "prompt(message, default);")
+    @JSBody(params = { "message", "defaultValue" }, script = "prompt(message, defaultValue);")
     public static native String prompt(String message, String defaultValue);
 
     @JSBody(params = { "handler", "delay" }, script = "return setTimeout(handler, delay);")