diff --git a/src/proto_http.c b/src/proto_http.c
index fb5c0858e..e6107ee23 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -12414,7 +12414,7 @@ static int sample_conv_url_dec(const struct arg *args, struct sample *smp, void
 	/* Add final \0 required by url_decode(), and convert the input string. */
 	smp->data.u.str.str[smp->data.u.str.len] = '\0';
 	smp->data.u.str.len = url_decode(smp->data.u.str.str);
-	return 1;
+	return (smp->data.u.str.len >= 0);
 }
 
 static int smp_conv_req_capture(const struct arg *args, struct sample *smp, void *private)