diff --git a/lib/Checker/UndefBranchChecker.cpp b/lib/Checker/UndefBranchChecker.cpp
new file mode 100644
index 0000000..e047b18
--- /dev/null
+++ b/lib/Checker/UndefBranchChecker.cpp
@@ -0,0 +1,117 @@
+//=== UndefBranchChecker.cpp -----------------------------------*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines UndefBranchChecker, which checks for undefined branch
+// condition.
+//
+//===----------------------------------------------------------------------===//
+
+#include "GRExprEngineInternalChecks.h"
+#include "clang/Checker/PathSensitive/Checker.h"
+
+using namespace clang;
+
+namespace {
+
+class UndefBranchChecker : public Checker {
+  BuiltinBug *BT;
+
+  struct FindUndefExpr {
+    GRStateManager& VM;
+    const GRState* St;
+
+    FindUndefExpr(GRStateManager& V, const GRState* S) : VM(V), St(S) {}
+
+    Expr* FindExpr(Expr* Ex) {
+      if (!MatchesCriteria(Ex))
+        return 0;
+
+      for (Stmt::child_iterator I=Ex->child_begin(), E=Ex->child_end();I!=E;++I)
+        if (Expr* ExI = dyn_cast_or_null<Expr>(*I)) {
+          Expr* E2 = FindExpr(ExI);
+          if (E2) return E2;
+        }
+
+      return Ex;
+    }
+
+    bool MatchesCriteria(Expr* Ex) { return St->getSVal(Ex).isUndef(); }
+  };
+
+public:
+  UndefBranchChecker() : BT(0) {}
+  static void *getTag();
+  void VisitBranchCondition(GRBranchNodeBuilder &Builder, GRExprEngine &Eng,
+                            Stmt *Condition, void *tag);
+};
+
+}
+
+void clang::RegisterUndefBranchChecker(GRExprEngine &Eng) {
+  Eng.registerCheck(new UndefBranchChecker());
+}
+
+void *UndefBranchChecker::getTag() {
+  static int x;
+  return &x;
+}
+
+void UndefBranchChecker::VisitBranchCondition(GRBranchNodeBuilder &Builder, 
+                                              GRExprEngine &Eng,
+                                              Stmt *Condition, void *tag) {
+  const GRState *state = Builder.getState();
+  SVal X = state->getSVal(Condition);
+  if (X.isUndef()) {
+    ExplodedNode *N = Builder.generateNode(state, true);
+    if (N) {
+      N->markAsSink();
+      if (!BT)
+        BT = new BuiltinBug("Branch condition evaluates to a garbage value");
+
+      // What's going on here: we want to highlight the subexpression of the
+      // condition that is the most likely source of the "uninitialized
+      // branch condition."  We do a recursive walk of the condition's
+      // subexpressions and roughly look for the most nested subexpression
+      // that binds to Undefined.  We then highlight that expression's range.
+      BlockEdge B = cast<BlockEdge>(N->getLocation());
+      Expr* Ex = cast<Expr>(B.getSrc()->getTerminatorCondition());
+      assert (Ex && "Block must have a terminator.");
+
+      // Get the predecessor node and check if is a PostStmt with the Stmt
+      // being the terminator condition.  We want to inspect the state
+      // of that node instead because it will contain main information about
+      // the subexpressions.
+      assert (!N->pred_empty());
+
+      // Note: any predecessor will do.  They should have identical state,
+      // since all the BlockEdge did was act as an error sink since the value
+      // had to already be undefined.
+      ExplodedNode *PrevN = *N->pred_begin();
+      ProgramPoint P = PrevN->getLocation();
+      const GRState* St = N->getState();
+
+      if (PostStmt* PS = dyn_cast<PostStmt>(&P))
+        if (PS->getStmt() == Ex)
+          St = PrevN->getState();
+
+      FindUndefExpr FindIt(Eng.getStateManager(), St);
+      Ex = FindIt.FindExpr(Ex);
+
+      // Emit the bug report.
+      EnhancedBugReport *R = new EnhancedBugReport(*BT, BT->getDescription(),N);
+      R->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, Ex);
+      R->addRange(Ex->getSourceRange());
+
+      Eng.getBugReporter().EmitReport(R);
+    }
+
+    Builder.markInfeasible(true);
+    Builder.markInfeasible(false);
+  }
+}