diff --git a/astrbot/core/provider/sources/gsv_selfhosted_source.py b/astrbot/core/provider/sources/gsv_selfhosted_source.py
index f4cac0ce1e..ac11a93c7d 100644
--- a/astrbot/core/provider/sources/gsv_selfhosted_source.py
+++ b/astrbot/core/provider/sources/gsv_selfhosted_source.py
@@ -33,7 +33,9 @@ def __init__(
 
         # TTS 请求的默认参数，移除前缀gsv_
         self.default_params: dict = {
-            key.removeprefix("gsv_"): str(value).lower()
+            key.removeprefix("gsv_"): (
+                str(value).lower() if isinstance(value, bool) else str(value)
+            )
             for key, value in provider_config.get("gsv_default_parms", {}).items()
         }
         self.timeout = provider_config.get("timeout", 60)
diff --git a/tests/unit/test_gsv_selfhosted_source.py b/tests/unit/test_gsv_selfhosted_source.py
new file mode 100644
index 0000000000..4e2c20ab07
--- /dev/null
+++ b/tests/unit/test_gsv_selfhosted_source.py
@@ -0,0 +1,24 @@
+import pytest
+
+import astrbot.api  # noqa: F401  # Initialize API before provider adapters.
+from astrbot.core.provider.sources.gsv_selfhosted_source import ProviderGSVTTS
+
+
+@pytest.mark.parametrize(
+    ("key", "value", "expected"),
+    [
+        ("ref_audio_path", "/Voices/Alice.WAV", "/Voices/Alice.WAV"),
+        ("prompt_text", "Hello NASA", "Hello NASA"),
+        ("streaming_mode", True, "true"),
+        ("parallel_infer", False, "false"),
+        ("top_k", 5, "5"),
+        ("speed_factor", 1.25, "1.25"),
+    ],
+)
+def test_synthesis_params_preserve_case_and_serialize_scalars(key, value, expected):
+    provider = ProviderGSVTTS({"gsv_default_parms": {f"gsv_{key}": value}}, {})
+
+    params = provider.build_synthesis_params("Read NASA aloud")
+
+    assert params[key] == expected
+    assert params["text"] == "Read NASA aloud"