diff --git a/test/testutil/driver.c b/test/testutil/driver.c
index 8d483336ff44f4f598bd003796983c1c9fed06c4..09907347f17204b4305f056625ec2b9bb2cdad1c 100644
--- a/test/testutil/driver.c
+++ b/test/testutil/driver.c
@@ -74,7 +74,7 @@ int subtest_level(void)
 }
 
 #ifndef OPENSSL_NO_CRYPTO_MDEBUG
-static int should_report_leaks()
+static int should_report_leaks(void)
 {
     /*
      * When compiled with enable-crypto-mdebug, OPENSSL_DEBUG_MEMORY=0