diff --git a/src/newgrf_industrytiles.cpp b/src/newgrf_industrytiles.cpp
index bfa1dbb88f..6983abd4ec 100644
--- a/src/newgrf_industrytiles.cpp
+++ b/src/newgrf_industrytiles.cpp
@@ -244,7 +244,7 @@ bool PerformIndustryTileSlopeCheck(TileIndex tile, const IndustryTileSpec *its,
 	if (its->grf_prop.grffile->grf_version < 7) {
 		return callback_res != 0;
 	}
-	if (callback_res != CALLBACK_FAILED) return true;
+	if (callback_res == CALLBACK_FAILED) return false;
 
 	switch (callback_res) {
 		case 0x400: return true;