diff --git a/tests/unit-test-client.c b/tests/unit-test-client.c
index 463f332..a099c80 100644
--- a/tests/unit-test-client.c
+++ b/tests/unit-test-client.c
@@ -593,7 +593,7 @@ int main(int argc, char *argv[])
     modbus_set_response_timeout(ctx, &old_response_timeout);
 
     /* Wait for data before flushing */
-    usleep(250000);
+    usleep(500000);
     modbus_flush(ctx);
 
     /** BAD RESPONSE **/