diff --git a/include/clang/Analysis/PathSensitive/GRExprEngine.h b/include/clang/Analysis/PathSensitive/GRExprEngine.h
index f625b9e..96a6d4a 100644
--- a/include/clang/Analysis/PathSensitive/GRExprEngine.h
+++ b/include/clang/Analysis/PathSensitive/GRExprEngine.h
@@ -211,7 +211,12 @@
   
   bool isUndefArg(const NodeTy* N) const {
     return N->isSink() &&
-           UndefArgs.find(const_cast<NodeTy*>(N)) != UndefArgs.end();
+      (UndefArgs.find(const_cast<NodeTy*>(N)) != UndefArgs.end() ||
+       MsgExprUndefArgs.find(const_cast<NodeTy*>(N)) != MsgExprUndefArgs.end());            
+  }
+  
+  bool isUndefReceiver(const NodeTy* N) const {
+    return N->isSink() && UndefReceivers.count(const_cast<NodeTy*>(N)) != 0;
   }
   
   typedef UndefBranchesTy::iterator undef_branch_iterator;
@@ -256,6 +261,23 @@
   undef_arg_iterator undef_arg_begin() { return UndefArgs.begin(); }
   undef_arg_iterator undef_arg_end() { return UndefArgs.end(); }  
   
+  undef_arg_iterator msg_expr_undef_arg_begin() {
+    return MsgExprUndefArgs.begin();
+  }
+  undef_arg_iterator msg_expr_undef_arg_end() {
+    return MsgExprUndefArgs.end();
+  }  
+  
+  typedef UndefReceiversTy::iterator undef_receivers_iterator;
+
+  undef_receivers_iterator undef_receivers_begin() {
+    return UndefReceivers.begin();
+  }
+  
+  undef_receivers_iterator undef_receivers_end() {
+    return UndefReceivers.end();
+  }
+  
   /// ProcessStmt - Called by GRCoreEngine. Used to generate new successor
   ///  nodes by processing the 'effects' of a block-level statement.  
   void ProcessStmt(Stmt* S, StmtNodeBuilder& builder);    
diff --git a/lib/Analysis/GRSimpleVals.cpp b/lib/Analysis/GRSimpleVals.cpp
index 8c538c0..b6e6b50 100644
--- a/lib/Analysis/GRSimpleVals.cpp
+++ b/lib/Analysis/GRSimpleVals.cpp
@@ -119,7 +119,7 @@
   EmitWarning(Diag, SrcMgr,
               CheckerState->null_derefs_begin(),
               CheckerState->null_derefs_end(),
-              "NULL pointer is dereferenced after it is checked for NULL.");
+              "Dereference of NULL pointer.");
   
   EmitWarning(Diag, SrcMgr,
               CheckerState->undef_derefs_begin(),
@@ -127,9 +127,9 @@
               "Dereference of undefined value.");
   
   EmitWarning(Diag, SrcMgr,
-              CheckerState->undef_derefs_begin(),
-              CheckerState->undef_derefs_end(),
-              "Dereference of undefined value.");
+              CheckerState->undef_branches_begin(),
+              CheckerState->undef_branches_end(),
+              "Branch condition evaluates to an uninitialized value.");
   
   EmitWarning(Diag, SrcMgr,
               CheckerState->explicit_bad_divides_begin(),
@@ -149,12 +149,18 @@
   EmitWarning(Diag, SrcMgr,
               CheckerState->undef_arg_begin(),
               CheckerState->undef_arg_end(),
-      "Pass-by-value argument in function or message expression is undefined.");
+              "Pass-by-value argument in function is undefined.");
   
   EmitWarning(Diag, SrcMgr,
-              CheckerState->undef_branches_begin(),
-              CheckerState->undef_branches_end(),
-      "Branch condition evaluates to an uninitialized value.");
+              CheckerState->msg_expr_undef_arg_begin(),
+              CheckerState->msg_expr_undef_arg_end(),
+              "Pass-by-value argument in message expression is undefined.");
+  
+  EmitWarning(Diag, SrcMgr,
+              CheckerState->undef_receivers_begin(),
+              CheckerState->undef_receivers_end(),
+              "Receiver in message expression is an uninitialized value.");
+
       
 #ifndef NDEBUG
   if (Visualize) CheckerState->ViewGraph(TrimGraph);