diff --git a/sec-gemini-python/sec_gemini/models/usage.py b/sec-gemini-python/sec_gemini/models/usage.py
index 799162d..a5a6d67 100644
--- a/sec-gemini-python/sec_gemini/models/usage.py
+++ b/sec-gemini-python/sec_gemini/models/usage.py
@@ -103,7 +103,6 @@ def tally(self, subusage: Usage) -> None:
       self.cached_token_count += subusage.cached_token_count
       self.thoughts_token_count += subusage.thoughts_token_count
       self.tool_use_prompt_token_count += subusage.tool_use_prompt_token_count
-      self.total_tokens += subusage.cached_token_count
 
   def __repr__(self):
     return (
diff --git a/sec-gemini-python/tests/test_usage.py b/sec-gemini-python/tests/test_usage.py
new file mode 100644
index 0000000..c1ff726
--- /dev/null
+++ b/sec-gemini-python/tests/test_usage.py
@@ -0,0 +1,62 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from sec_gemini.models.usage import Usage
+
+
+def test_tally_accumulates_usage_without_double_counting_cached_tokens():
+  aggregate = Usage()
+  subusage = Usage(
+    prompt_tokens=100,
+    generated_tokens=50,
+    total_tokens=150,
+    cached_token_count=30,
+    thoughts_token_count=10,
+    tool_use_prompt_token_count=5,
+  )
+
+  aggregate.tally(subusage)
+
+  assert aggregate.prompt_tokens == 100
+  assert aggregate.generated_tokens == 50
+  assert aggregate.total_tokens == 150
+  assert aggregate.cached_token_count == 30
+  assert aggregate.thoughts_token_count == 10
+  assert aggregate.tool_use_prompt_token_count == 5
+
+
+def test_tally_accumulates_multiple_usages():
+  aggregate = Usage()
+  aggregate.tally(
+    Usage(
+      prompt_tokens=10,
+      generated_tokens=5,
+      total_tokens=15,
+      cached_token_count=2,
+    )
+  )
+  aggregate.tally(
+    Usage(
+      prompt_tokens=20,
+      generated_tokens=10,
+      total_tokens=30,
+      cached_token_count=4,
+    )
+  )
+
+  assert aggregate.prompt_tokens == 30
+  assert aggregate.generated_tokens == 15
+  assert aggregate.total_tokens == 45
+  assert aggregate.cached_token_count == 6