diff --git a/x86_64/umac-nh-n.asm b/x86_64/umac-nh-n.asm
index 5faf6ddbc23cf1c3f66fcad075014620c2e0dbde..bcb994874ea87b16bbbd1fea7e8b4bebbff29b9c 100644
--- a/x86_64/umac-nh-n.asm
+++ b/x86_64/umac-nh-n.asm
@@ -47,7 +47,7 @@ C aligned.
 	.file "umac-nh-n.asm"
 	
 	C umac_nh_n(uint64_t *out, unsigned n, const uint32_t *key,
-	C	    size_t length, const uint8_t *msg)
+	C	    unsigned length, const uint8_t *msg)
 	.text
 	ALIGN(16)
 PROLOGUE(_nettle_umac_nh_n)
diff --git a/x86_64/umac-nh.asm b/x86_64/umac-nh.asm
index 544a19e06673f9cc4c5d627f21d93e1067d76f94..8e88df6a4fb4e8728b0d0d74e2ebf4fd6bf5acc4 100644
--- a/x86_64/umac-nh.asm
+++ b/x86_64/umac-nh.asm
@@ -34,7 +34,7 @@ C aligned.
 
 	.file "umac-nh.asm"
 	
-	C umac_nh(const uint32_t *key, size_t length, const uint8_t *msg)
+	C umac_nh(const uint32_t *key, unsigned length, const uint8_t *msg)
 	.text
 	ALIGN(16)
 PROLOGUE(_nettle_umac_nh)