diff --git a/src/compile.cpp b/src/compile.cpp
index 3a4bc7ed63..214cc7ba2c 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -8532,7 +8532,7 @@ class MyProcessor: public Processor {
       }
 
       Reference* r = new (t->m->heap->allocate(sizeof(Reference)))
-        Reference(o, &(t->reference));
+        Reference(o, &(t->reference), false);
 
       acquire(t, r);
 
diff --git a/src/jnienv.cpp b/src/jnienv.cpp
index 34f82efc65..f815497078 100644
--- a/src/jnienv.cpp
+++ b/src/jnienv.cpp
@@ -2157,7 +2157,7 @@ SetStaticDoubleField(Thread* t, jobject c, jfieldID field, jdouble v)
 }
 
 jobject JNICALL
-NewGlobalRef(Thread* t, jobject o)
+newGlobalRef(Thread* t, jobject o, bool weak)
 {
   ENTER(t, Thread::ActiveState);
 
@@ -2165,7 +2165,7 @@ NewGlobalRef(Thread* t, jobject o)
   
   if (o) {
     for (Reference* r = t->m->jniReferences; r; r = r->next) {
-      if (r->target == *o) {
+      if (r->target == *o and r->weak == weak) {
         acquire(t, r);
 
         return &(r->target);
@@ -2173,7 +2173,7 @@ NewGlobalRef(Thread* t, jobject o)
     }
 
     Reference* r = new (t->m->heap->allocate(sizeof(Reference)))
-      Reference(*o, &(t->m->jniReferences));
+      Reference(*o, &(t->m->jniReferences), weak);
 
     acquire(t, r);
 
@@ -2183,6 +2183,12 @@ NewGlobalRef(Thread* t, jobject o)
   }
 }
 
+jobject JNICALL
+NewGlobalRef(Thread* t, jobject o)
+{
+  return newGlobalRef(t, o, false);
+}
+
 void JNICALL
 DeleteGlobalRef(Thread* t, jobject r)
 {
@@ -2195,6 +2201,18 @@ DeleteGlobalRef(Thread* t, jobject r)
   }
 }
 
+jobject JNICALL
+NewWeakGlobalRef(Thread* t, jobject o)
+{
+  return newGlobalRef(t, o, true);
+}
+
+void JNICALL
+DeleteWeakGlobalRef(Thread* t, jobject r)
+{
+  DeleteGlobalRef(t, r);
+}
+
 jint JNICALL
 EnsureLocalCapacity(Thread*, jint)
 {
@@ -3166,8 +3184,9 @@ populateJNITables(JavaVMVTable* vmTable, JNIEnvVTable* envTable)
   envTable->SetStaticFloatField = local::SetStaticFloatField;
   envTable->SetStaticDoubleField = local::SetStaticDoubleField;
   envTable->NewGlobalRef = local::NewGlobalRef;
-  envTable->NewWeakGlobalRef = local::NewGlobalRef;
+  envTable->NewWeakGlobalRef = local::NewWeakGlobalRef;
   envTable->DeleteGlobalRef = local::DeleteGlobalRef;
+  envTable->DeleteWeakGlobalRef = local::DeleteWeakGlobalRef;
   envTable->EnsureLocalCapacity = local::EnsureLocalCapacity;
   envTable->ExceptionOccurred = local::ExceptionOccurred;
   envTable->ExceptionDescribe = local::ExceptionDescribe;
diff --git a/src/machine.cpp b/src/machine.cpp
index 0ff4539bf6..65213cd637 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -584,6 +584,16 @@ postVisit(Thread* t, Heap::Visitor* v)
       = m->tenuredWeakReferences;
     m->tenuredWeakReferences = firstNewTenuredWeakReference;
   }
+
+  for (Reference* r = m->jniReferences; r; r = r->next) {
+    if (r->weak) {
+      if (m->heap->status(r->target) == Heap::Unreachable) {
+        r->target = 0;
+      } else {
+        v->visit(&(r->target));
+      }
+    }
+  }
 }
 
 void
@@ -4142,7 +4152,9 @@ visitRoots(Machine* m, Heap::Visitor* v)
   }
 
   for (Reference* r = m->jniReferences; r; r = r->next) {
-    v->visit(&(r->target));
+    if (not r->weak) {
+      v->visit(&(r->target));
+    }
   }
 }
 
diff --git a/src/machine.h b/src/machine.h
index 8f2a6f4cf7..44b239c690 100644
--- a/src/machine.h
+++ b/src/machine.h
@@ -1215,11 +1215,12 @@ noop();
 
 class Reference {
  public:
-  Reference(object target, Reference** handle):
+  Reference(object target, Reference** handle, bool weak):
     target(target),
     next(*handle),
     handle(handle),
-    count(0)
+    count(0),
+    weak(weak)
   {
     if (next) {
       next->handle = &next;
@@ -1231,6 +1232,7 @@ class Reference {
   Reference* next;
   Reference** handle;
   unsigned count;
+  bool weak;
 };
 
 class Classpath;