diff --git a/lib/crc32.c b/lib/crc32.c
index af938ab..9a907d4 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -53,7 +53,7 @@
 #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
 
 /* implements slicing-by-4 or slicing-by-8 algorithm */
-static inline u32
+static inline u32 __pure
 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
 {
 # ifdef __LITTLE_ENDIAN