diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 36ba8d0..ec09481 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -195,9 +195,9 @@
   return getType()->getContext();
 }
 
-unsigned Function::getInstructionCount() {
+unsigned Function::getInstructionCount() const {
   unsigned NumInstrs = 0;
-  for (BasicBlock &BB : BasicBlocks)
+  for (const BasicBlock &BB : BasicBlocks)
     NumInstrs += std::distance(BB.instructionsWithoutDebug().begin(),
                                BB.instructionsWithoutDebug().end());
   return NumInstrs;