diff --git a/com.ibm.wala.cast.js.test/examples-src/tests/prototype_contamination_bug.js b/com.ibm.wala.cast.js.test/examples-src/tests/prototype_contamination_bug.js
new file mode 100644
index 000000000..3115c8f03
--- /dev/null
+++ b/com.ibm.wala.cast.js.test/examples-src/tests/prototype_contamination_bug.js
@@ -0,0 +1,28 @@
+function A(){
+	
+}
+A.prototype.foo = function foo_of_A(){
+	console.log("foo_of_A");
+}
+
+function B(){
+	
+}
+B.prototype.foo = function foo_of_B(){
+	console.log("foo_of_B");
+}
+
+function test1(){
+	var a = new A
+	console.log("calling foo_of_A");
+	a.foo() 
+}
+
+function test2(){
+	var b = new B
+	console.log("calling foo_of_B");
+	b.foo() 
+}
+
+test1()
+test2()
\ No newline at end of file
diff --git a/com.ibm.wala.cast.js.test/harness-src/com/ibm/wala/cast/js/test/TestSimpleCallGraphShape.java b/com.ibm.wala.cast.js.test/harness-src/com/ibm/wala/cast/js/test/TestSimpleCallGraphShape.java
index 20eb3bdb4..eb5368119 100644
--- a/com.ibm.wala.cast.js.test/harness-src/com/ibm/wala/cast/js/test/TestSimpleCallGraphShape.java
+++ b/com.ibm.wala.cast.js.test/harness-src/com/ibm/wala/cast/js/test/TestSimpleCallGraphShape.java
@@ -243,4 +243,21 @@ public abstract class TestSimpleCallGraphShape extends TestJSCallGraphShape {
     verifyGraphAssertions(CG, assertionsForMultivar);
   }
 
+  private static final Object[][] assertionsForPrototypeContamination = new Object[][] {
+    new Object[] { ROOT, new String[] { "tests/prototype_contamination_bug.js" } },
+    new Object[] { "suffix:test1", 
+        new String[] { "suffix:foo_of_A"} },
+    new Object[] { "suffix:test2", 
+        new String[] { "suffix:foo_of_B"} }
+  };
+
+  @Test public void testProtoypeContamination() throws IOException, IllegalArgumentException, CancelException {
+    CallGraph CG = Util.makeScriptCG("tests", "prototype_contamination_bug.js");
+    verifyGraphAssertions(CG, assertionsForPrototypeContamination);
+    verifyNoEdges(CG, "suffix:test1", "suffix:foo_of_B");
+    verifyNoEdges(CG, "suffix:test2", "suffix:foo_of_A");
+    
+  }
+  
+  
 }
diff --git a/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/ipa/callgraph/JavaScriptConstructTargetSelector.java b/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/ipa/callgraph/JavaScriptConstructTargetSelector.java
index d69d22832..0227b2022 100644
--- a/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/ipa/callgraph/JavaScriptConstructTargetSelector.java
+++ b/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/ipa/callgraph/JavaScriptConstructTargetSelector.java
@@ -349,11 +349,11 @@ public class JavaScriptConstructTargetSelector implements MethodTargetSelector {
     
     S.addStatement(insts.NewInstruction(5, NewSiteReference.make(S.getNextProgramCounter(), cls.getReference())));
 
-    S.addStatement(insts.PutInstruction(5, 4, "prototype"));
-    S.getNextProgramCounter();
-    
     S.addStatement(insts.NewInstruction(7, NewSiteReference.make(S.getNextProgramCounter(), JavaScriptTypes.Object)));
 
+    S.addStatement(insts.PutInstruction(7, 4, "prototype"));
+    S.getNextProgramCounter();
+    
     S.addStatement(insts.PutInstruction(5, 7, "prototype"));
     S.getNextProgramCounter();
     
diff --git a/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/translator/PropertyReadExpander.java b/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/translator/PropertyReadExpander.java
index 6bb9cbc7c..f32ef4100 100644
--- a/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/translator/PropertyReadExpander.java
+++ b/com.ibm.wala.cast.js/source/com/ibm/wala/cast/js/translator/PropertyReadExpander.java
@@ -81,17 +81,36 @@ public class PropertyReadExpander extends CAstRewriter<PropertyReadExpander.Rewr
   private CAstNode makeConstRead(CAstNode receiver, CAstNode element, RewriteContext context) {
     String receiverTemp = TEMP_NAME + (readTempCounter++);
     String elt = (String) element.getValue();
-
-    if (context.inAssignment()) {
-      context.setAssign(Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeConstant(elt));
+    if (elt.equals("prototype")){
+      return Ast.makeNode(CAstNode.BLOCK_EXPR, 
+                Ast.makeNode(CAstNode.OBJECT_REF,
+                  receiver, 
+        		  Ast.makeConstant("prototype")));
+    } else {
+      
+      if (context.inAssignment()) {
+        context.setAssign(Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeConstant(elt));
+      }
+      
+      return Ast.makeNode(CAstNode.BLOCK_EXPR, 
+          Ast.makeNode(CAstNode.DECL_STMT, 
+              Ast.makeConstant(new InternalCAstSymbol(receiverTemp,false, false)), 
+              receiver), 
+          Ast.makeNode(CAstNode.LOOP, 
+              Ast.makeNode(CAstNode.UNARY_EXPR, 
+            		  CAstOperator.OP_NOT, 
+            		  Ast.makeNode(CAstNode.IS_DEFINED_EXPR, 
+            		      Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), 
+            		      Ast.makeConstant(elt))), 
+              Ast.makeNode(CAstNode.ASSIGN, 
+                  Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), 
+                  Ast.makeNode(CAstNode.OBJECT_REF,
+                      Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), 
+                      Ast.makeConstant("prototype")))), 
+          Ast.makeNode(CAstNode.OBJECT_REF, 
+        		  Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), 
+        		  Ast.makeConstant(elt)));
     }
-
-    return Ast.makeNode(CAstNode.BLOCK_EXPR, Ast.makeNode(CAstNode.DECL_STMT, Ast.makeConstant(new InternalCAstSymbol(receiverTemp,
-        false, false)), receiver), Ast.makeNode(CAstNode.LOOP, Ast.makeNode(CAstNode.UNARY_EXPR, CAstOperator.OP_NOT, Ast.makeNode(
-        CAstNode.IS_DEFINED_EXPR, Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeConstant(elt))), Ast
-        .makeNode(CAstNode.ASSIGN, Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeNode(CAstNode.OBJECT_REF,
-            Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeConstant("prototype")))), Ast.makeNode(
-        CAstNode.OBJECT_REF, Ast.makeNode(CAstNode.VAR, Ast.makeConstant(receiverTemp)), Ast.makeConstant(elt)));
   }
 
   private CAstNode makeVarRead(CAstNode receiver, CAstNode element, RewriteContext context) {
diff --git a/com.ibm.wala.cast.test/harness-src/com/ibm/wala/cast/test/TestCallGraphShape.java b/com.ibm.wala.cast.test/harness-src/com/ibm/wala/cast/test/TestCallGraphShape.java
index ec6ab241d..17d893010 100644
--- a/com.ibm.wala.cast.test/harness-src/com/ibm/wala/cast/test/TestCallGraphShape.java
+++ b/com.ibm.wala.cast.test/harness-src/com/ibm/wala/cast/test/TestCallGraphShape.java
@@ -104,6 +104,29 @@ public abstract class TestCallGraphShape extends WalaTestCase {
     }
   }
 
+
+  /**
+   * Verifies that non of the nodes that match the source description has an edge to any of the nodes that match the destination
+   * description. (Used for checking for false connections in the callgraph)
+   * 
+   * @param CG
+   * @param sourceDescription
+   * @param destDescription
+   */
+  protected void verifyNoEdges(CallGraph CG, String sourceDescription, String destDescription) {
+    Collection sources = getNodes(CG, sourceDescription);
+    Collection dests = getNodes(CG, destDescription);
+    for (Object source : sources) {
+      for (Object dest : dests) {
+        for (Iterator<CGNode> i = CG.getSuccNodes((CGNode) source); i.hasNext();) {
+          if (i.next().equals(dest)) {
+            Assert.fail("Found a link from " + source + " to " + dest);
+          }
+        }
+      }
+    }
+  }
+  
   protected static final Object ROOT = new Object();
 
   protected abstract Collection getNodes(CallGraph CG, String functionIdentifier);