diff --git a/src/common/tortls.c b/src/common/tortls.c
index f4d4ec8b65..aaf2fdaacb 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -160,7 +160,7 @@ static int tor_tls_object_ex_data_index = -1;
 
 /** Helper: Allocate tor_tls_object_ex_data_index. */
 static void
-tor_tls_allocate_tor_tls_object_ex_data_index()
+tor_tls_allocate_tor_tls_object_ex_data_index(void)
 {
   if (tor_tls_object_ex_data_index == -1) {
     tor_tls_object_ex_data_index =