diff --git a/library/sha512.c b/library/sha512.c
index b1947f1..d0faba9 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -418,7 +418,7 @@
     { "" }
 };
 
-static const int sha512_test_buflen[3] =
+static const size_t sha512_test_buflen[3] =
 {
     3, 112, 1000
 };