diff --git a/src/edit.c b/src/edit.c
index 983f1ac..d3fffc5 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -4607,7 +4607,7 @@
 }
 
     static void
-ins_s_left()
+ins_s_left(void)
 {
     int end_change = dont_sync_undo == FALSE; // end undoable change
 #ifdef FEAT_FOLDING
@@ -4676,7 +4676,7 @@
 }
 
     static void
-ins_s_right()
+ins_s_right(void)
 {
     int end_change = dont_sync_undo == FALSE; // end undoable change
 #ifdef FEAT_FOLDING