diff --git a/grepWinNP3/sktoolslib_mod/TextFile.cpp b/grepWinNP3/sktoolslib_mod/TextFile.cpp
index b681e1b59..c6fa45b81 100644
--- a/grepWinNP3/sktoolslib_mod/TextFile.cpp
+++ b/grepWinNP3/sktoolslib_mod/TextFile.cpp
@@ -22,6 +22,7 @@
 #include "PathUtils.h"
 #include "maxpath.h"
 #include <memory>
+#include <cassert>
 
 static wchar_t WideCharSwap(wchar_t nValue)
 {