diff --git a/fastapi/openapi/utils.py b/fastapi/openapi/utils.py
index 808646cc2..729e4972d 100644
--- a/fastapi/openapi/utils.py
+++ b/fastapi/openapi/utils.py
@@ -366,11 +366,17 @@ def get_openapi_path(
                         )
                     else:
                         response_schema = {}
-                operation.setdefault("responses", {}).setdefault(
+
+                route_responses = {str(k): v for k, v in route.responses.items()}
+                if status_code not in route_responses or not route_responses.get(
                     status_code, {}
-                ).setdefault("content", {}).setdefault(route_response_media_type, {})[
-                    "schema"
-                ] = response_schema
+                ).get("superimpose"):
+                    operation.setdefault("responses", {}).setdefault(
+                        status_code, {}
+                    ).setdefault("content", {}).setdefault(
+                        route_response_media_type, {}
+                    )["schema"] = response_schema
+
             if route.responses:
                 operation_responses = operation.setdefault("responses", {})
                 for (
@@ -379,6 +385,7 @@ def get_openapi_path(
                 ) in route.responses.items():
                     process_response = additional_response.copy()
                     process_response.pop("model", None)
+                    process_response.pop("superimpose", None)
                     status_code_key = str(additional_status_code).upper()
                     if status_code_key == "DEFAULT":
                         status_code_key = "default"
diff --git a/tests/test_additional_responses_default_media_type.py b/tests/test_additional_responses_default_media_type.py
new file mode 100644
index 000000000..8e92356e8
--- /dev/null
+++ b/tests/test_additional_responses_default_media_type.py
@@ -0,0 +1,154 @@
+"""
+This test is about the possibility of superimposing an additional response's media_type
+over the default route's response class's media_type.
+"""
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from pydantic import BaseModel
+from starlette.status import HTTP_200_OK, HTTP_500_INTERNAL_SERVER_ERROR
+
+app = FastAPI()
+client = TestClient(app)
+
+
+class Error(BaseModel):
+    status: str
+    title: str
+
+
+@app.get(
+    "/a",
+    responses={
+        HTTP_200_OK: {"superimpose": True, "content": {"text/event-stream": {}}},
+        HTTP_500_INTERNAL_SERVER_ERROR: {"description": "Error", "model": Error},
+    },
+)
+def a():
+    pass  # pragma: no cover
+
+
+@app.get(
+    "/b",
+    responses={
+        str(HTTP_200_OK): {"content": {"text/event-stream": {}}},
+        HTTP_500_INTERNAL_SERVER_ERROR: {"description": "Error", "model": Error},
+    },
+)
+def b():
+    pass  # pragma: no cover
+
+
+@app.get(
+    "/c",
+    responses={
+        HTTP_500_INTERNAL_SERVER_ERROR: {"description": "Error", "model": Error}
+    },
+)
+def c():
+    pass  # pragma: no cover
+
+
+@app.get("/d")
+def d():
+    pass  # pragma: no cover
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "openapi": "3.1.0",
+        "info": {"title": "FastAPI", "version": "0.1.0"},
+        "paths": {
+            "/a": {
+                "get": {
+                    "summary": "A",
+                    "operationId": "a_a_get",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"text/event-stream": {}},
+                        },
+                        "500": {
+                            "description": "Error",
+                            "content": {
+                                "application/json": {
+                                    "schema": {"$ref": "#/components/schemas/Error"}
+                                }
+                            },
+                        },
+                    },
+                }
+            },
+            "/b": {
+                "get": {
+                    "summary": "B",
+                    "operationId": "b_b_get",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {
+                                "application/json": {"schema": {}},
+                                "text/event-stream": {},
+                            },
+                        },
+                        "500": {
+                            "description": "Error",
+                            "content": {
+                                "application/json": {
+                                    "schema": {"$ref": "#/components/schemas/Error"}
+                                }
+                            },
+                        },
+                    },
+                }
+            },
+            "/c": {
+                "get": {
+                    "summary": "C",
+                    "operationId": "c_c_get",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        },
+                        "500": {
+                            "description": "Error",
+                            "content": {
+                                "application/json": {
+                                    "schema": {"$ref": "#/components/schemas/Error"}
+                                }
+                            },
+                        },
+                    },
+                }
+            },
+            "/d": {
+                "get": {
+                    "summary": "D",
+                    "operationId": "d_d_get",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        }
+                    },
+                }
+            },
+        },
+        "components": {
+            "schemas": {
+                "Error": {
+                    "properties": {
+                        "status": {"type": "string", "title": "Status"},
+                        "title": {"type": "string", "title": "Title"},
+                    },
+                    "type": "object",
+                    "required": ["status", "title"],
+                    "title": "Error",
+                }
+            }
+        },
+    }