diff --git a/runtime/native/java_lang_Runtime.cc b/runtime/native/java_lang_Runtime.cc
index f6149ff..636be5d 100644
--- a/runtime/native/java_lang_Runtime.cc
+++ b/runtime/native/java_lang_Runtime.cc
@@ -92,12 +92,12 @@
 }
 
 static JNINativeMethod gMethods[] = {
-  NATIVE_METHOD(Runtime, freeMemory, "()J"),
+  NATIVE_METHOD(Runtime, freeMemory, "!()J"),
   NATIVE_METHOD(Runtime, gc, "()V"),
-  NATIVE_METHOD(Runtime, maxMemory, "()J"),
+  NATIVE_METHOD(Runtime, maxMemory, "!()J"),
   NATIVE_METHOD(Runtime, nativeExit, "(I)V"),
   NATIVE_METHOD(Runtime, nativeLoad, "(Ljava/lang/String;Ljava/lang/ClassLoader;Ljava/lang/String;)Ljava/lang/String;"),
-  NATIVE_METHOD(Runtime, totalMemory, "()J"),
+  NATIVE_METHOD(Runtime, totalMemory, "!()J"),
 };
 
 void register_java_lang_Runtime(JNIEnv* env) {