diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
index 31b0a5c6780f4..75a6e1a6b5a89 100644
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -27,7 +27,7 @@
 // Declare the __builtin_strlen intrinsic for MSVC so it can be used in
 // constexpr context.
 #if defined(_MSC_VER)
-extern "C" constexpr size_t __builtin_strlen(const char *);
+extern "C" size_t __builtin_strlen(const char *);
 #endif
 
 namespace llvm {
@@ -80,7 +80,8 @@ namespace llvm {
     static constexpr size_t strLen(const char *Str) {
 #if __cplusplus > 201402L
       return std::char_traits<char>::length(Str);
-#elif __has_builtin(__builtin_strlen) || defined(__GNUC__) || defined(_MSC_VER)
+#elif __has_builtin(__builtin_strlen) || defined(__GNUC__) || \
+    (defined(_MSC_VER) && _MSC_VER >= 1920)
       return __builtin_strlen(Str);
 #else
       const char *Begin = Str;