diff --git a/libs/core/langchain_core/utils/_merge.py b/libs/core/langchain_core/utils/_merge.py
index e300259819e30..4200ca304d6a0 100644
--- a/libs/core/langchain_core/utils/_merge.py
+++ b/libs/core/langchain_core/utils/_merge.py
@@ -64,6 +64,8 @@ def merge_dicts(left: dict[str, Any], *others: dict[str, Any]) -> dict[str, Any]
                 merged[right_k] = merge_lists(merged[right_k], right_v)
             elif merged[right_k] == right_v:
                 continue
+            elif isinstance(merged[right_k], int):
+                merged[right_k] += right_v
             else:
                 msg = (
                     f"Additional kwargs key {right_k} already exists in left dict and "
diff --git a/libs/core/tests/unit_tests/utils/test_utils.py b/libs/core/tests/unit_tests/utils/test_utils.py
index 258b447409b97..ae2404abd19e7 100644
--- a/libs/core/tests/unit_tests/utils/test_utils.py
+++ b/libs/core/tests/unit_tests/utils/test_utils.py
@@ -9,6 +9,7 @@
 from pydantic import SecretStr
 
 from langchain_core import utils
+from langchain_core.outputs import GenerationChunk
 from langchain_core.utils import (
     check_package_version,
     from_env,
@@ -395,3 +396,10 @@ class OhMy(BaseModel):
 
     with pytest.raises(ValueError, match="Did not find FOOFOOFOOBAR"):
         OhMy()
+
+
+def test_generation_chunk_addition_type_error() -> None:
+    chunk1 = GenerationChunk(text="", generation_info={"len": 0})
+    chunk2 = GenerationChunk(text="Non-empty text", generation_info={"len": 14})
+    result = chunk1 + chunk2
+    assert result == GenerationChunk(text="Non-empty text", generation_info={"len": 14})