diff --git a/src/connectrpc/_client_shared.py b/src/connectrpc/_client_shared.py
index d0df033..bfd3e49 100644
--- a/src/connectrpc/_client_shared.py
+++ b/src/connectrpc/_client_shared.py
@@ -22,14 +22,12 @@
 def prepare_get_params(
     codec: Codec, request_data: bytes, headers: HTTPHeaders
 ) -> dict[str, str]:
-    params = {
-        "connect": f"v{CONNECT_PROTOCOL_VERSION}",
-        "message": base64.urlsafe_b64encode(request_data).decode("ascii"),
-        "base64": "1",
-        "encoding": codec.name(),
-    }
+    # Follow order in spec: https://connectrpc.com/docs/protocol/#unary-get-request
+    params: dict[str, str] = {"connect": f"v{CONNECT_PROTOCOL_VERSION}", "base64": "1"}
     if "content-encoding" in headers:
         params["compression"] = headers.pop("content-encoding")
+    params["encoding"] = codec.name()
+    params["message"] = base64.urlsafe_b64encode(request_data).decode("ascii")
     return params
 
 
diff --git a/test/test_client_shared.py b/test/test_client_shared.py
new file mode 100644
index 0000000..179ecf5
--- /dev/null
+++ b/test/test_client_shared.py
@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from urllib.parse import urlencode
+
+from pyqwest import Headers as HTTPHeaders
+
+from connectrpc._client_shared import prepare_get_params
+from connectrpc.codec import proto_binary_codec
+
+
+def test_prepare_get_params_order() -> None:
+    headers = HTTPHeaders([("content-encoding", "gzip")])
+    params = prepare_get_params(proto_binary_codec(), b"hello", headers)
+    assert list(params.keys()) == [
+        "connect",
+        "base64",
+        "compression",
+        "encoding",
+        "message",
+    ]
+    assert "content-encoding" not in headers
+    query = urlencode(params)
+    expected_prefix = "connect=v1&base64=1&compression=gzip&encoding=proto&message="
+    assert query.startswith(expected_prefix)
+
+
+def test_prepare_get_params_order_without_compression() -> None:
+    params = prepare_get_params(proto_binary_codec(), b"hello", HTTPHeaders([]))
+    assert list(params.keys()) == ["connect", "base64", "encoding", "message"]