diff --git a/library/sha256.c b/library/sha256.c
index 0e24d69..b765697 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -380,7 +380,7 @@
     { "" }
 };
 
-static const int sha256_test_buflen[3] =
+static const size_t sha256_test_buflen[3] =
 {
     3, 56, 1000
 };