diff --git a/llvm/lib/Support/FileCheck.cpp b/llvm/lib/Support/FileCheck.cpp
index 143f7a4..9310a79 100644
--- a/llvm/lib/Support/FileCheck.cpp
+++ b/llvm/lib/Support/FileCheck.cpp
@@ -125,7 +125,7 @@
 
 // StringRef holding all characters considered as horizontal whitespaces by
 // FileCheck input canonicalization.
-StringRef SpaceChars = " \t";
+constexpr StringLiteral SpaceChars = " \t";
 
 // Parsing helper function that strips the first character in S and returns it.
 static char popFront(StringRef &S) {