diff --git a/openjdkjvm/OpenjdkJvm.cc b/openjdkjvm/OpenjdkJvm.cc
index 8d0200c..7a388c9 100644
--- a/openjdkjvm/OpenjdkJvm.cc
+++ b/openjdkjvm/OpenjdkJvm.cc
@@ -434,36 +434,37 @@
   }
 }
 
-JNIEXPORT jint JVM_IHashCode(JNIEnv* env ATTRIBUTE_UNUSED,
+JNIEXPORT __attribute__((noreturn)) jint JVM_IHashCode(JNIEnv* env ATTRIBUTE_UNUSED,
                              jobject javaObject ATTRIBUTE_UNUSED) {
   UNIMPLEMENTED(FATAL) << "JVM_IHashCode is not implemented";
-  return 0;
+  UNREACHABLE();
 }
 
-JNIEXPORT jlong JVM_NanoTime(JNIEnv* env ATTRIBUTE_UNUSED, jclass unused ATTRIBUTE_UNUSED) {
+JNIEXPORT __attribute__((noreturn)) jlong JVM_NanoTime(JNIEnv* env ATTRIBUTE_UNUSED, jclass unused ATTRIBUTE_UNUSED) {
   UNIMPLEMENTED(FATAL) << "JVM_NanoTime is not implemented";
-  return 0L;
+  UNREACHABLE();
 }
 
-JNIEXPORT void JVM_ArrayCopy(JNIEnv* /* env */, jclass /* unused */, jobject /* javaSrc */,
+JNIEXPORT __attribute__((noreturn)) void JVM_ArrayCopy(JNIEnv* /* env */, jclass /* unused */, jobject /* javaSrc */,
                              jint /* srcPos */, jobject /* javaDst */, jint /* dstPos */,
                              jint /* length */) {
   UNIMPLEMENTED(FATAL) << "JVM_ArrayCopy is not implemented";
+  UNREACHABLE();
 }
 
-JNIEXPORT jint JVM_FindSignal(const char* name ATTRIBUTE_UNUSED) {
+JNIEXPORT __attribute__((noreturn)) jint JVM_FindSignal(const char* name ATTRIBUTE_UNUSED) {
   LOG(FATAL) << "JVM_FindSignal is not implemented";
-  return 0;
+  UNREACHABLE();
 }
 
-JNIEXPORT void* JVM_RegisterSignal(jint signum ATTRIBUTE_UNUSED, void* handler ATTRIBUTE_UNUSED) {
+JNIEXPORT __attribute__((noreturn)) void* JVM_RegisterSignal(jint signum ATTRIBUTE_UNUSED, void* handler ATTRIBUTE_UNUSED) {
   LOG(FATAL) << "JVM_RegisterSignal is not implemented";
-  return nullptr;
+  UNREACHABLE();
 }
 
-JNIEXPORT jboolean JVM_RaiseSignal(jint signum ATTRIBUTE_UNUSED) {
+JNIEXPORT __attribute__((noreturn)) jboolean JVM_RaiseSignal(jint signum ATTRIBUTE_UNUSED) {
   LOG(FATAL) << "JVM_RaiseSignal is not implemented";
-  return JNI_FALSE;
+  UNREACHABLE();
 }
 
 JNIEXPORT __attribute__((noreturn))  void JVM_Halt(jint code) {