diff --git a/tests/kat_sig_stfl.c b/tests/kat_sig_stfl.c
index c81e54c00a..9c01539fb1 100644
--- a/tests/kat_sig_stfl.c
+++ b/tests/kat_sig_stfl.c
@@ -357,7 +357,9 @@ OQS_STATUS sig_stfl_kat(const char *method_name, const char *katfile) {
 	OQS_MEM_insecure_free(msg);
 	OQS_MEM_insecure_free(msg_rand);
 	OQS_SIG_STFL_free(sig);
-	fclose(fp_rsp);
+    if (fp_rsp != NULL) {
+        fclose(fp_rsp);
+    }
 	return ret;
 }