diff --git a/lib/VMCore/Dominators.cpp b/lib/VMCore/Dominators.cpp
index 6d0e23d6427..1f172145c3b 100644
--- a/lib/VMCore/Dominators.cpp
+++ b/lib/VMCore/Dominators.cpp
@@ -52,10 +52,16 @@ void DominatorTree::print(raw_ostream &OS, const Module *) const {
   DT->print(OS);
 }
 
-// dominates - Return true if A dominates B. This performs the
+// dominates - Return true if A dominates a use in B. This performs the
 // special checks necessary if A and B are in the same basic block.
 bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
   const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
+  
+  // If A is an invoke instruction, its value is only available in this normal
+  // successor block.
+  if (const InvokeInst *II = dyn_cast<InvokeInst>(A))
+    BBA = II->getNormalDest();
+  
   if (BBA != BBB) return dominates(BBA, BBB);
   
   // It is not possible to determine dominance between two PHI nodes 
diff --git a/test/Transforms/Mem2Reg/crash.ll b/test/Transforms/Mem2Reg/crash.ll
new file mode 100644
index 00000000000..ce795aaaca4
--- /dev/null
+++ b/test/Transforms/Mem2Reg/crash.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -mem2reg -S
+; PR5023
+
+declare i32 @bar()
+
+define i32 @foo() {
+entry:
+  %whichFlag = alloca i32
+  %A = invoke i32 @bar()
+          to label %invcont2 unwind label %lpad86
+
+invcont2:
+  store i32 %A, i32* %whichFlag
+  br label %bb15
+
+bb15:
+  %B = load i32* %whichFlag
+  ret i32 %B
+
+lpad86:
+  br label %bb15
+  
+}
+