diff --git a/lib/Checker/UndefinedAssignmentChecker.cpp b/lib/Checker/UndefinedAssignmentChecker.cpp
new file mode 100644
index 0000000..7c33c1d
--- /dev/null
+++ b/lib/Checker/UndefinedAssignmentChecker.cpp
@@ -0,0 +1,79 @@
+//===--- UndefinedAssignmentChecker.h ---------------------------*- C++ -*--==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This defines UndefinedAssginmentChecker, a builtin check in GRExprEngine that
+// checks for assigning undefined values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "GRExprEngineInternalChecks.h"
+#include "clang/Checker/PathSensitive/CheckerVisitor.h"
+#include "clang/Checker/BugReporter/BugReporter.h"
+
+using namespace clang;
+
+namespace {
+class UndefinedAssignmentChecker
+  : public CheckerVisitor<UndefinedAssignmentChecker> {
+  BugType *BT;
+public:
+  UndefinedAssignmentChecker() : BT(0) {}
+  static void *getTag();
+  virtual void PreVisitBind(CheckerContext &C, const Stmt *AssignE,
+                            const Stmt *StoreE, SVal location,
+                            SVal val);
+};
+}
+
+void clang::RegisterUndefinedAssignmentChecker(GRExprEngine &Eng){
+  Eng.registerCheck(new UndefinedAssignmentChecker());
+}
+
+void *UndefinedAssignmentChecker::getTag() {
+  static int x = 0;
+  return &x;
+}
+
+void UndefinedAssignmentChecker::PreVisitBind(CheckerContext &C,
+                                              const Stmt *AssignE,
+                                              const Stmt *StoreE,
+                                              SVal location,
+                                              SVal val) {
+  if (!val.isUndef())
+    return;
+
+  ExplodedNode *N = C.GenerateSink();
+
+  if (!N)
+    return;
+
+  if (!BT)
+    BT = new BuiltinBug("Assigned value is garbage or undefined");
+
+  // Generate a report for this bug.
+  EnhancedBugReport *R = new EnhancedBugReport(*BT, BT->getName(), N);
+
+  if (AssignE) {
+    const Expr *ex = 0;
+
+    if (const BinaryOperator *B = dyn_cast<BinaryOperator>(AssignE))
+      ex = B->getRHS();
+    else if (const DeclStmt *DS = dyn_cast<DeclStmt>(AssignE)) {
+      const VarDecl* VD = dyn_cast<VarDecl>(DS->getSingleDecl());
+      ex = VD->getInit();
+    }
+    if (ex) {
+      R->addRange(ex->getSourceRange());
+      R->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, ex);
+    }
+  }
+
+  C.EmitReport(R);
+}  
+