diff --git a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
index 25b068591e9a40a42a5e62a4613f05b2081e2e77..193002b14d7f66ac9c1b6942f79d662760278ac7 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
@@ -19,7 +19,7 @@ static int libbpf_debug_print(enum libbpf_print_level level,
 	log_buf = va_arg(args, char *);
 	if (!log_buf)
 		goto out;
-	if (strstr(log_buf, err_str) == 0)
+	if (err_str && strstr(log_buf, err_str) == 0)
 		found = true;
 out:
 	printf(format, log_buf);