diff --git a/pdf.c b/pdf.c
index 69bc056951fb9be5a46b08b6df791b3a47c2f13f..052069632e55e96287e9638ef7e03063f0e967a1 100644
--- a/pdf.c
+++ b/pdf.c
@@ -13,8 +13,8 @@
 #define REP(P,N)	h_repeat_n(P, N)
 #define IGN(P)		h_ignore(P)
 #define LIT(S)		h_ignore(h_literal(S))
-#define IN(STR)		h_in(STR, sizeof(STR) - 1)
-#define NOT_IN(STR)	h_not_in(STR, sizeof STR - 1)
+#define IN(STR)		h_in((const uint8_t *)(STR), sizeof(STR) - 1)
+#define NOT_IN(STR)	h_not_in((const uint8_t *)(STR), sizeof STR - 1)
 
 
 /*