diff --git a/library/rsa.c b/library/rsa.c
index 88c1cf1..58746e5 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1521,7 +1521,7 @@
     size_t olen;
     unsigned char *p = sig;
     unsigned char salt[MBEDTLS_MD_MAX_SIZE];
-    unsigned int slen, hlen, offset = 0;
+    size_t slen, hlen, offset = 0;
     int ret;
     size_t msb;
     const mbedtls_md_info_t *md_info;