diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
index 4e9bfa40a5d0..68d2deff959e 100644
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_ADT_STRINGREF_H
 #define LLVM_ADT_STRINGREF_H
 
+#include <cassert>
 #include <cstring>
 #include <string>