diff --git a/x86_64/sha512-compress.asm b/x86_64/sha512-compress.asm
index 3b0391a6bdb0268b6eddd80f434b63b7121314fb..d54ebda33373b477de093287d284ab9f3c539828 100644
--- a/x86_64/sha512-compress.asm
+++ b/x86_64/sha512-compress.asm
@@ -111,7 +111,7 @@ define(<NOEXPN>, <
 >)
 
 	C void
-	C _nettle_sha512_compress(uint32_t *state, const uint8_t *input, const uint32_t *k)
+	C _nettle_sha512_compress(uint64_t *state, const uint8_t *input, const uint64_t *k)
 
 	.text
 	ALIGN(4)