(Fmodify_frame_parameters):

Call frame-set-background-mode after changing the background color
on non-window non-dos branch.

src/frame.c

@@ -2313,6 +2313,12 @@ enabled such bindings for that variable with `make-variable-frame-local'.  */)
 	  prop = parms[i];
 	  val = values[i];
 	  store_frame_param (f, prop, val);
+
+	  /* Changing the background color might change the background
+	     mode, so that we have to load new defface specs.
+	     Call frame-set-background-mode to do that.  */
+	  if (EQ (prop, Qbackground_color))
+	    call1 (Qframe_set_background_mode, frame);
 	}
     }