diff --git a/langchain/memory/kg.py b/langchain/memory/kg.py
index 7d23f60b..b0aaa4c0 100644
--- a/langchain/memory/kg.py
+++ b/langchain/memory/kg.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List
+from typing import Any, Dict, List, Type, Union
 
 from pydantic import BaseModel, Field
 
@@ -12,7 +12,12 @@ from langchain.memory.prompt import (
 )
 from langchain.memory.utils import get_prompt_input_key
 from langchain.prompts.base import BasePromptTemplate
-from langchain.schema import BaseLanguageModel, SystemMessage, get_buffer_string
+from langchain.schema import (
+    BaseLanguageModel,
+    BaseMessage,
+    SystemMessage,
+    get_buffer_string,
+)
 
 
 class ConversationKGMemory(BaseChatMemory, BaseModel):
@@ -29,6 +34,7 @@ class ConversationKGMemory(BaseChatMemory, BaseModel):
     knowledge_extraction_prompt: BasePromptTemplate = KNOWLEDGE_TRIPLE_EXTRACTION_PROMPT
     entity_extraction_prompt: BasePromptTemplate = ENTITY_EXTRACTION_PROMPT
     llm: BaseLanguageModel
+    summary_message_cls: Type[BaseMessage] = SystemMessage
     """Number of previous utterances to include in the context."""
     memory_key: str = "history"  #: :meta private:
 
@@ -40,12 +46,15 @@ class ConversationKGMemory(BaseChatMemory, BaseModel):
             knowledge = self.kg.get_entity_knowledge(entity)
             if knowledge:
                 summaries[entity] = ". ".join(knowledge) + "."
+        context: Union[str, List]
         if summaries:
             summary_strings = [
                 f"On {entity}: {summary}" for entity, summary in summaries.items()
             ]
             if self.return_messages:
-                context: Any = [SystemMessage(content=text) for text in summary_strings]
+                context = [
+                    self.summary_message_cls(content=text) for text in summary_strings
+                ]
             else:
                 context = "\n".join(summary_strings)
         else:
diff --git a/langchain/memory/summary.py b/langchain/memory/summary.py
index 082e3a43..4f9b27e1 100644
--- a/langchain/memory/summary.py
+++ b/langchain/memory/summary.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List
+from typing import Any, Dict, List, Type
 
 from pydantic import BaseModel, root_validator
 
@@ -19,6 +19,7 @@ class SummarizerMixin(BaseModel):
     ai_prefix: str = "AI"
     llm: BaseLanguageModel
     prompt: BasePromptTemplate = SUMMARY_PROMPT
+    summary_message_cls: Type[BaseMessage] = SystemMessage
 
     def predict_new_summary(
         self, messages: List[BaseMessage], existing_summary: str
@@ -50,7 +51,7 @@ class ConversationSummaryMemory(BaseChatMemory, SummarizerMixin, BaseModel):
     def load_memory_variables(self, inputs: Dict[str, Any]) -> Dict[str, Any]:
         """Return history buffer."""
         if self.return_messages:
-            buffer: Any = [SystemMessage(content=self.buffer)]
+            buffer: Any = [self.summary_message_cls(content=self.buffer)]
         else:
             buffer = self.buffer
         return {self.memory_key: buffer}
diff --git a/langchain/memory/summary_buffer.py b/langchain/memory/summary_buffer.py
index 9f0f5c6b..ae29f38a 100644
--- a/langchain/memory/summary_buffer.py
+++ b/langchain/memory/summary_buffer.py
@@ -4,7 +4,7 @@ from pydantic import BaseModel, root_validator
 
 from langchain.memory.chat_memory import BaseChatMemory
 from langchain.memory.summary import SummarizerMixin
-from langchain.schema import BaseMessage, SystemMessage, get_buffer_string
+from langchain.schema import BaseMessage, get_buffer_string
 
 
 class ConversationSummaryBufferMemory(BaseChatMemory, SummarizerMixin, BaseModel):
@@ -12,6 +12,7 @@ class ConversationSummaryBufferMemory(BaseChatMemory, SummarizerMixin, BaseModel
 
     max_token_limit: int = 2000
     moving_summary_buffer: str = ""
+    summary_message_role: str = "system"
     memory_key: str = "history"
 
     @property
@@ -31,7 +32,7 @@ class ConversationSummaryBufferMemory(BaseChatMemory, SummarizerMixin, BaseModel
         buffer = self.buffer
         if self.moving_summary_buffer != "":
             first_messages: List[BaseMessage] = [
-                SystemMessage(content=self.moving_summary_buffer)
+                self.summary_message_cls(content=self.moving_summary_buffer)
             ]
             buffer = first_messages + buffer
         if self.return_messages: