diff --git a/src/requests/sessions.py b/src/requests/sessions.py
index 731550de88..93a9f09929 100644
--- a/src/requests/sessions.py
+++ b/src/requests/sessions.py
@@ -482,7 +482,7 @@ def prepare_request(self, request):
 
         p = PreparedRequest()
         p.prepare(
-            method=request.method.upper(),
+            method=(request.method or "GET").upper(),
             url=request.url,
             files=request.files,
             data=request.data,
diff --git a/tests/test_requests.py b/tests/test_requests.py
index 75d2deff2e..9b4c411c8f 100644
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -1225,6 +1225,25 @@ def test_prepare_request_with_bytestring_url(self):
         prep = s.prepare_request(req)
         assert prep.url == "https://httpbin.org/"
 
+    def test_prepare_request_with_none_method(self):
+        """Test that prepare_request handles None method correctly.
+        
+        When Request.method is None,
+        prepare_request() should default to "GET" instead of crashing.
+        """
+        # Create a Request without specifying method (defaults to None)
+        req = requests.Request(url="https://httpbin.org/")
+        assert req.method is None
+        
+        s = requests.Session()
+        
+        # After the fix, this should work and default to GET
+        prep = s.prepare_request(req)
+        
+        # Verify the method defaults to GET
+        assert prep.method == "GET"
+        assert prep.url == "https://httpbin.org/"
+
     def test_request_with_bytestring_host(self, httpbin):
         s = requests.Session()
         resp = s.request(