diff --git a/tests/providers/test_image_generation.py b/tests/providers/test_image_generation.py
index 3bee376d8..eea3a3fe6 100644
--- a/tests/providers/test_image_generation.py
+++ b/tests/providers/test_image_generation.py
@@ -390,6 +390,17 @@ async def test_minimax_payload_and_response_with_reference_image(tmp_path: Path)
     assert body["subject_reference"][0]["image_file"].startswith("data:image/png;base64,")
 
 
+@pytest.mark.asyncio
+async def test_minimax_base64_response_uses_detected_mime() -> None:
+    raw_b64 = base64.b64encode(JPEG_BYTES).decode("ascii")
+    fake = FakeClient(FakeResponse({"data": {"image_base64": [raw_b64]}}))
+    client = MiniMaxImageGenerationClient(api_key="sk-mm-test", client=fake)  # type: ignore[arg-type]
+
+    response = await client.generate(prompt="draw", model="image-01")
+
+    assert response.images == [f"data:image/jpeg;base64,{raw_b64}"]
+
+
 # ---------------------------------------------------------------------------
 # StepFun (阶跃星辰)
 # ---------------------------------------------------------------------------