diff --git a/libs/core/langchain_core/prompts/prompt.py b/libs/core/langchain_core/prompts/prompt.py
index 8c9732b2daf..36ed47250ce 100644
--- a/libs/core/langchain_core/prompts/prompt.py
+++ b/libs/core/langchain_core/prompts/prompt.py
@@ -138,8 +138,8 @@ class PromptTemplate(StringPromptTemplate):
         # Allow for easy combining
         if isinstance(other, PromptTemplate):
             if self.template_format != other.template_format:
-                msg = "Cannot add two templates of different formats"
-                raise ValueError(msg) 
+                msg = "Cannot add templates of different formats"
+                raise ValueError(msg)
             input_variables = list(
                 set(self.input_variables) | set(other.input_variables)
             )
@@ -160,7 +160,10 @@ class PromptTemplate(StringPromptTemplate):
                 validate_template=validate_template,
             )
         if isinstance(other, str):
-            prompt = PromptTemplate.from_template(other, template_format=self.template_format)
+            prompt = PromptTemplate.from_template(
+                other,
+                template_format=self.template_format,
+            )
             return self + prompt
         msg = f"Unsupported operand type for +: {type(other)}"
         raise NotImplementedError(msg)
diff --git a/libs/core/tests/unit_tests/prompts/test_prompt.py b/libs/core/tests/unit_tests/prompts/test_prompt.py
index 12315e1a264..3d09882fd69 100644
--- a/libs/core/tests/unit_tests/prompts/test_prompt.py
+++ b/libs/core/tests/unit_tests/prompts/test_prompt.py
@@ -684,7 +684,7 @@ def test_prompt_with_template_variable_name_jinja2() -> None:
 
 
 def test_prompt_template_add_with_with_another_format():
-    with pytest.raises(match=r"Cannot add two templates"):
+    with pytest.raises(match=r"Cannot add templates"):
         PromptTemplate.from_template("This is a {template}") + PromptTemplate.from_template("So {{this}} is", template_format="mustache")