diff --git a/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c b/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
index cf8ad99696..6576e681c3 100644
--- a/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
+++ b/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
@@ -1137,6 +1137,22 @@ ProcessVariable (
     return EFI_SECURITY_VIOLATION;
   }
   
+  //
+  // A time-based authenticated variable and a count-based authenticated variable
+  // can't be updated by each other.
+  // 
+  if (Variable->CurrPtr != NULL) {    
+    if (((Attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS) != 0) &&
+        ((Variable->CurrPtr->Attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) != 0)) {
+      return EFI_SECURITY_VIOLATION;      
+    }
+    
+    if (((Attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) != 0) && 
+        ((Variable->CurrPtr->Attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS) != 0)) {
+      return EFI_SECURITY_VIOLATION;      
+    }
+  }
+    
   //
   // Process Time-based Authenticated variable.
   //