diff --git a/src/nfa/limex_compile.cpp b/src/nfa/limex_compile.cpp
index 2010728d..75b7c72b 100644
--- a/src/nfa/limex_compile.cpp
+++ b/src/nfa/limex_compile.cpp
@@ -242,7 +242,7 @@ bool isLimitedTransition(int from, int to, int maxshift) {
 
 // Fill a bit mask
 template<class Mask>
-void maskFill(Mask &m, char c) {
+void maskFill(Mask &m, u8 c) {
     memset(&m, c, sizeof(m));
 }