diff --git a/lib/sha-1.c b/lib/sha-1.c
index f30f3ed6..6020c227 100644
--- a/lib/sha-1.c
+++ b/lib/sha-1.c
@@ -92,7 +92,8 @@ struct sha1_ctxt {
 #ifndef unsupported
 
 /* constant table */
-static unsigned int _K[] = { 0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6 };
+static const unsigned int _K[] =
+			{ 0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6 };
 #define	K(t)	_K[(t) / 20]
 
 #define	F0(b, c, d)	(((b) & (c)) | ((~(b)) & (d)))