diff --git a/src/crangler/scanner.l b/src/crangler/scanner.l
index d45027b3cbd..19e4f377b4d 100644
--- a/src/crangler/scanner.l
+++ b/src/crangler/scanner.l
@@ -54,6 +54,16 @@ PreprocessorDirective           {PreprocessorStart}[^\r\n]*
 static int isatty(int) { return 0; }
 #endif
 
+#if defined _MSC_VER
+// signed/unsigned mismatch
+#pragma warning(disable:4365)
+// macro re-definition: flex conditonally defines INT32_MAX et al. and thus
+// they are set before library headers get to define them
+#pragma warning(disable:4005)
+#endif
+
+#include <util/pragma_wsign_compare.def>
+#include <util/pragma_wnull_conversion.def>
 #include <util/pragma_wdeprecated_register.def>
 
 #include <set>