diff --git a/include/llvm/Analysis/CFG.h b/include/llvm/Analysis/CFG.h
index 7c4df780198..35165f4061f 100644
--- a/include/llvm/Analysis/CFG.h
+++ b/include/llvm/Analysis/CFG.h
@@ -40,7 +40,7 @@ void FindFunctionBackedges(
 /// Search for the specified successor of basic block BB and return its position
 /// in the terminator instruction's list of successors.  It is an error to call
 /// this with a block that is not a successor.
-unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ);
+unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ);
 
 /// Return true if the specified edge is a critical edge. Critical edges are
 /// edges from a block with multiple successors to a block with multiple
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 041fcb6313b..0dfd57d3cb6 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -69,8 +69,9 @@ void llvm::FindFunctionBackedges(const Function &F,
 /// and return its position in the terminator instruction's list of
 /// successors.  It is an error to call this with a block that is not a
 /// successor.
-unsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) {
-  TerminatorInst *Term = BB->getTerminator();
+unsigned llvm::GetSuccessorNumber(const BasicBlock *BB,
+    const BasicBlock *Succ) {
+  const TerminatorInst *Term = BB->getTerminator();
 #ifndef NDEBUG
   unsigned e = Term->getNumSuccessors();
 #endif