diff --git a/src/newgrf_station.cpp b/src/newgrf_station.cpp
index e86d40214a..8ef375c4cf 100644
--- a/src/newgrf_station.cpp
+++ b/src/newgrf_station.cpp
@@ -694,8 +694,9 @@ CommandCost PerformStationTileSlopeCheck(TileIndex north_tile, TileIndex cur_til
 	/* Failed callback means success. */
 	if (cb_res == CALLBACK_FAILED) return CommandCost();
 
-	/* The meaning of bit 10 is inverted in the result of this callback. */
-	return GetErrorMessageFromLocationCallbackResult(ToggleBit(cb_res, 10), statspec->grf_prop.grffile->grfid, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
+	/* The meaning of bit 10 is inverted for a grf version < 8. */
+	if (statspec->grf_prop.grffile->grf_version < 8) ToggleBit(cb_res, 10);
+	return GetErrorMessageFromLocationCallbackResult(cb_res, statspec->grf_prop.grffile->grfid, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 }
 
 
diff --git a/src/object_cmd.cpp b/src/object_cmd.cpp
index d073852141..e613c7705b 100644
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@@ -241,9 +241,10 @@ CommandCost CmdBuildObject(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 
 			if (callback == CALLBACK_FAILED) {
 				cost.AddCost(CheckBuildableTile(t, 0, allowed_z, false, false));
-			} else if (callback != 0) {
-				/* The meaning of bit 10 is inverted in the result of this callback. */
-				return GetErrorMessageFromLocationCallbackResult(ToggleBit(callback, 10), spec->grf_prop.grffile->grfid, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
+			} else {
+				/* The meaning of bit 10 is inverted for a grf version < 8. */
+				if (spec->grf_prop.grffile->grf_version < 8) ToggleBit(callback, 10);
+				return GetErrorMessageFromLocationCallbackResult(callback, spec->grf_prop.grffile->grfid, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 			}
 		}