diff --git a/include/llvm/ADT/StringRef.h b/include/llvm/ADT/StringRef.h
index 3e1e24c1ea4..fd5b28e8fc1 100644
--- a/include/llvm/ADT/StringRef.h
+++ b/include/llvm/ADT/StringRef.h
@@ -175,7 +175,7 @@ namespace llvm {
     /// transform one of the given strings into the other. If zero,
     /// the strings are identical.
     unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
-                           unsigned MaxEditDistance = 0);
+                           unsigned MaxEditDistance = 0) const;
 
     /// str - Get the contents as an std::string.
     std::string str() const {
diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index d7a0bfa4100..ee49ca80ffd 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -85,7 +85,7 @@ int StringRef::compare_numeric(StringRef RHS) const {
 // Compute the edit distance between the two given strings.
 unsigned StringRef::edit_distance(llvm::StringRef Other,
                                   bool AllowReplacements,
-                                  unsigned MaxEditDistance) {
+                                  unsigned MaxEditDistance) const {
   return llvm::ComputeEditDistance(
       llvm::ArrayRef<char>(data(), size()),
       llvm::ArrayRef<char>(Other.data(), Other.size()),