diff --git a/cmd/multiproduct_kati/main.go b/cmd/multiproduct_kati/main.go
index 9cb75fa..6a3d579 100644
--- a/cmd/multiproduct_kati/main.go
+++ b/cmd/multiproduct_kati/main.go
@@ -393,6 +393,9 @@
 
 	config := build.NewConfig(ctx, flag.Args()...)
 	config.Environment().Set("OUT_DIR", outDir)
+	if !*keepArtifacts {
+		config.Environment().Set("EMPTY_NINJA_FILE", "true")
+	}
 	build.FindSources(ctx, config, mpctx.Finder)
 	config.Lunch(ctx, product, *buildVariant)
 
@@ -413,12 +416,7 @@
 				log.Fatalf("Error zipping artifacts: %v", err)
 			}
 		}
-		if *incremental {
-			// Save space, Kati doesn't notice
-			if f := config.KatiBuildNinjaFile(); f != "" {
-				os.Truncate(f, 0)
-			}
-		} else {
+		if !*incremental {
 			os.RemoveAll(outDir)
 		}
 	}()