diff --git a/langchain/document_loaders/git.py b/langchain/document_loaders/git.py
index 39a9235e..15576762 100644
--- a/langchain/document_loaders/git.py
+++ b/langchain/document_loaders/git.py
@@ -28,7 +28,7 @@ class GitLoader(BaseLoader):
 
     def load(self) -> List[Document]:
         try:
-            from git import Blob, Repo
+            from git import Blob, Repo  # type: ignore
         except ImportError as ex:
             raise ImportError(
                 "Could not import git python package. "
diff --git a/langchain/tools/sql_database/tool.py b/langchain/tools/sql_database/tool.py
index a9ac6981..3921b43a 100644
--- a/langchain/tools/sql_database/tool.py
+++ b/langchain/tools/sql_database/tool.py
@@ -1,6 +1,7 @@
 # flake8: noqa
 """Tools for interacting with a SQL database."""
-from pydantic import BaseModel, Extra, Field, validator
+from pydantic import BaseModel, Extra, Field, validator, root_validator
+from typing import Any, Dict
 
 from langchain.chains.llm import LLMChain
 from langchain.prompts import PromptTemplate
@@ -81,28 +82,29 @@ class QueryCheckerTool(BaseSQLDatabaseTool, BaseTool):
 
     template: str = QUERY_CHECKER
     llm: BaseLLM
-    llm_chain: LLMChain = Field(
-        default_factory=lambda: LLMChain(
-            llm=QueryCheckerTool.llm,
-            prompt=PromptTemplate(
-                template=QueryCheckerTool.template, input_variables=["query", "dialect"]
-            ),
-        )
-    )
+    llm_chain: LLMChain = Field(init=False)
     name = "query_checker_sql_db"
     description = """
     Use this tool to double check if your query is correct before executing it.
     Always use this tool before executing a query with query_sql_db!
     """
 
-    @validator("llm_chain")
-    def validate_llm_chain_input_variables(cls, llm_chain: LLMChain) -> LLMChain:
-        """Make sure the LLM chain has the correct input variables."""
-        if llm_chain.prompt.input_variables != ["query", "dialect"]:
+    @root_validator(pre=True)
+    def initialize_llm_chain(cls, values: Dict[str, Any]) -> Dict[str, Any]:
+        if "llm_chain" not in values:
+            values["llm_chain"] = LLMChain(
+                llm=values.get("llm"),
+                prompt=PromptTemplate(
+                    template=QUERY_CHECKER, input_variables=["query", "dialect"]
+                ),
+            )
+
+        if values["llm_chain"].prompt.input_variables != ["query", "dialect"]:
             raise ValueError(
                 "LLM chain for QueryCheckerTool must have input variables ['query', 'dialect']"
             )
-        return llm_chain
+
+        return values
 
     def _run(self, query: str) -> str:
         """Use the LLM to check the query."""
diff --git a/tests/unit_tests/agents/test_sql.py b/tests/unit_tests/agents/test_sql.py
new file mode 100644
index 00000000..89b8f90d
--- /dev/null
+++ b/tests/unit_tests/agents/test_sql.py
@@ -0,0 +1,18 @@
+from langchain.agents import create_sql_agent
+from langchain.agents.agent_toolkits import SQLDatabaseToolkit
+from langchain.sql_database import SQLDatabase
+from tests.unit_tests.llms.fake_llm import FakeLLM
+
+
+def test_create_sql_agent() -> None:
+    db = SQLDatabase.from_uri("sqlite:///:memory:")
+    queries = {"foo": "Final Answer: baz"}
+    llm = FakeLLM(queries=queries, sequential_responses=True)
+    toolkit = SQLDatabaseToolkit(db=db, llm=llm)
+
+    agent_executor = create_sql_agent(
+        llm=llm,
+        toolkit=toolkit,
+    )
+
+    assert agent_executor.run("hello") == "baz"
diff --git a/tests/unit_tests/llms/fake_llm.py b/tests/unit_tests/llms/fake_llm.py
index 263bc2b6..cc12a7ca 100644
--- a/tests/unit_tests/llms/fake_llm.py
+++ b/tests/unit_tests/llms/fake_llm.py
@@ -1,5 +1,7 @@
 """Fake LLM wrapper for testing purposes."""
-from typing import Any, List, Mapping, Optional
+from typing import Any, List, Mapping, Optional, cast
+
+from pydantic import validator
 
 from langchain.llms.base import LLM
 
@@ -8,6 +10,18 @@ class FakeLLM(LLM):
     """Fake LLM wrapper for testing purposes."""
 
     queries: Optional[Mapping] = None
+    sequential_responses: Optional[bool] = False
+    response_index: int = 0
+
+    @validator("queries", always=True)
+    def check_queries_required(
+        cls, queries: Optional[Mapping], values: Mapping[str, Any]
+    ) -> Optional[Mapping]:
+        if values.get("sequential_response") and not queries:
+            raise ValueError(
+                "queries is required when sequential_response is set to True"
+            )
+        return queries
 
     @property
     def _llm_type(self) -> str:
@@ -15,7 +29,9 @@ class FakeLLM(LLM):
         return "fake"
 
     def _call(self, prompt: str, stop: Optional[List[str]] = None) -> str:
-        """First try to lookup in queries, else return 'foo' or 'bar'."""
+        if self.sequential_responses:
+            return self._get_next_response_in_sequence
+
         if self.queries is not None:
             return self.queries[prompt]
         if stop is None:
@@ -26,3 +42,10 @@ class FakeLLM(LLM):
     @property
     def _identifying_params(self) -> Mapping[str, Any]:
         return {}
+
+    @property
+    def _get_next_response_in_sequence(self) -> str:
+        queries = cast(Mapping, self.queries)
+        response = queries[list(queries.keys())[self.response_index]]
+        self.response_index = self.response_index + 1
+        return response