diff --git a/crypto/sha2.c b/crypto/sha2.c
index 26162e8..00a1af3 100644
--- a/crypto/sha2.c
+++ b/crypto/sha2.c
@@ -208,7 +208,7 @@
 	size_t fill;
 	uint32_t left;
 
-	if (length <= 0)
+	if (length == 0)
 		return;
 
 	left = ctx->total[0] & 0x3F;