diff --git a/programs/pkey/rsa_sign.c b/programs/pkey/rsa_sign.c
index 344d030..c283514 100644
--- a/programs/pkey/rsa_sign.c
+++ b/programs/pkey/rsa_sign.c
@@ -36,7 +36,8 @@
 int main( int argc, char *argv[] )
 {
     FILE *f;
-    int ret, i;
+    int ret;
+    size_t i;
     rsa_context rsa;
     unsigned char hash[20];
     unsigned char buf[512];