diff --git a/src/crypto/axtls_sha1.c b/src/crypto/axtls_sha1.c
index b44fe7fe8..62ff878a0 100644
--- a/src/crypto/axtls_sha1.c
+++ b/src/crypto/axtls_sha1.c
@@ -19,7 +19,7 @@ struct crypto_algorithm sha1_algorithm = {
 	.name		= "sha1",
 	.ctxsize	= SHA1_CTX_SIZE,
 	.blocksize	= 64,
-	.digestsize	= SHA1_SIZE,
+	.digestsize	= SHA1_DIGEST_SIZE,
 	.init		= sha1_init,
 	.encode		= sha1_update,
 	.final		= sha1_final,
diff --git a/src/include/gpxe/sha1.h b/src/include/gpxe/sha1.h
index 0a811018c..2d6e90ddf 100644
--- a/src/include/gpxe/sha1.h
+++ b/src/include/gpxe/sha1.h
@@ -6,6 +6,7 @@
 struct crypto_algorithm;
 
 #define SHA1_CTX_SIZE sizeof ( SHA1_CTX )
+#define SHA1_DIGEST_SIZE SHA1_SIZE
 
 extern struct crypto_algorithm sha1_algorithm;