diff --git a/bsd/extern.h b/bsd/extern.h
index 4c93453..0d14722 100644
--- a/bsd/extern.h
+++ b/bsd/extern.h
@@ -1,4 +1,5 @@
 #include <sys/types.h>
+#include <limits.h>
 
 int memnchr(const void *, int, size_t);
 void free_argv(char **);