diff --git a/js/src/jit-test/tests/basic/primitive-proto-properties.js b/js/src/jit-test/tests/basic/primitive-proto-properties.js
new file mode 100644
index 000000000000..ea012e40e6d3
--- /dev/null
+++ b/js/src/jit-test/tests/basic/primitive-proto-properties.js
@@ -0,0 +1,47 @@
+function shadowing() {
+    Object.prototype.x = 1;
+
+    for (var i = 0; i < 20; i++) {
+        var x = "a".x;
+        assertEq(x, i <= 15 ? 1 : "hello");
+
+        if (i == 15) {
+            String.prototype.x = "hello";
+        }
+    }
+
+    delete Object.prototype.x;
+}
+
+function deleted() {
+    String.prototype.y = 1;
+
+    for (var i = 0; i < 20; i++) {
+        var y = "a".y;
+        assertEq(y, i <= 15 ? 1 : undefined);
+
+        if (i == 15) {
+            delete String.prototype.y;
+        }
+    }
+
+    delete String.prototype.y;
+}
+
+
+function notdefined() {
+    for (var i = 0; i < 20; i++) {
+        var z = "a".z;
+        assertEq(z, i <= 15 ? undefined : "test");
+
+        if (i == 15) {
+            String.prototype.z = "test";
+        }
+    }
+
+    delete String.prototype.z;
+}
+
+shadowing();
+deleted();
+notdefined();
diff --git a/js/src/jit/CacheIR.cpp b/js/src/jit/CacheIR.cpp
index 8baf10a76428..cc39fa5a28e0 100644
--- a/js/src/jit/CacheIR.cpp
+++ b/js/src/jit/CacheIR.cpp
@@ -854,22 +854,26 @@ GetPropIRGenerator::tryAttachPrimitive(ValOperandId valId, HandleId id)
     if (!proto)
         return false;
 
-    // Instantiate this property, for use during Ion compilation.
-    if (IsIonEnabled(cx_))
-        EnsureTrackPropertyTypes(cx_, proto, id);
-
-    // For now, only look for properties directly set on the prototype.
-    Shape* shape = proto->lookup(cx_, id);
-    if (!shape || !shape->hasSlot() || !shape->hasDefaultGetter())
+    RootedShape shape(cx_);
+    RootedNativeObject holder(cx_);
+    NativeGetPropCacheability type = CanAttachNativeGetProp(cx_, proto, id, &holder, &shape, pc_,
+                                                            engine_, canAttachGetter_,
+                                                            isTemporarilyUnoptimizable_);
+    if (type != CanAttachReadSlot)
         return false;
 
+    if (holder) {
+        // Instantiate this property, for use during Ion compilation.
+        if (IsIonEnabled(cx_))
+            EnsureTrackPropertyTypes(cx_, holder, id);
+    }
+
     writer.guardType(valId, primitiveType);
     maybeEmitIdGuard(id);
 
     ObjOperandId protoId = writer.loadObject(proto);
-    writer.guardShape(protoId, proto->lastProperty());
-    EmitLoadSlotResult(writer, protoId, proto, shape);
-    writer.typeMonitorResult();
+    EmitReadSlotResult(writer, proto, holder, shape, protoId);
+    EmitReadSlotReturn(writer, proto, holder, shape);
     return true;
 }