diff --git a/contrib/coccinelle/strbuf.cocci b/contrib/coccinelle/strbuf.cocci
index 1d580e49b0..6fe8727421 100644
--- a/contrib/coccinelle/strbuf.cocci
+++ b/contrib/coccinelle/strbuf.cocci
@@ -29,8 +29,9 @@ cocci.include_match("%" not in fmt)
 
 @@
 expression E1, E2;
+format F =~ "s";
 @@
-- strbuf_addf(E1, "%s", E2);
+- strbuf_addf(E1, "%@F@", E2);
 + strbuf_addstr(E1, E2);
 
 @@