diff --git a/fastapi/security/http.py b/fastapi/security/http.py
index d9de1f0d7..e26d85932 100644
--- a/fastapi/security/http.py
+++ b/fastapi/security/http.py
@@ -75,10 +75,11 @@ class HTTPBase(SecurityBase):
         description: Optional[str] = None,
         auto_error: bool = True,
     ):
-        self.model = HTTPBaseModel(scheme=scheme, description=description)
+        self.model: HTTPBaseModel = HTTPBaseModel(
+            scheme=scheme, description=description
+        )
         self.scheme_name = scheme_name or self.__class__.__name__
         self.auto_error = auto_error
-        self.scheme = scheme
 
     async def __call__(
         self, request: Request
@@ -90,7 +91,7 @@ class HTTPBase(SecurityBase):
                 raise HTTPException(
                     status_code=HTTP_401_UNAUTHORIZED,
                     detail="Not authenticated",
-                    headers={"WWW-Authenticate": self.scheme},
+                    headers={"WWW-Authenticate": self.model.scheme},
                 )
 
             else: