diff --git a/tests/tests.c b/tests/tests.c
index e1df47a..b4a33e2 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -266,7 +266,7 @@ static int p_encrypt_decrypt(void)
             fsize = 0;
         }
         if (DEBUG) {
-            printf(YELLOW "\tFile size:" BLUE " %lu bytes\n", fsize);
+            printf(YELLOW "\tFile size:" BLUE " %" PRIu64 " bytes\n", fsize);
         }
         fillrand(data, fsize);
         fillrand(key, KEY_SIZE);
@@ -428,7 +428,7 @@ int p_password_enc_dec(void)
         }
 
         if (DEBUG) {
-            printf(YELLOW "\tFile size:" BLUE " %lu bytes\n", fsize);
+            printf(YELLOW "\tFile size:" BLUE " %" PRIu64 " bytes\n", fsize);
         }
 
         fillrand(data, fsize);