diff --git a/src/js/game/hud/parts/base_toolbar.js b/src/js/game/hud/parts/base_toolbar.js
index 3db6dfcb..75862c41 100644
--- a/src/js/game/hud/parts/base_toolbar.js
+++ b/src/js/game/hud/parts/base_toolbar.js
@@ -1,6 +1,6 @@
 import { gMetaBuildingRegistry } from "../../../core/global_registries";
 import { Signal, STOP_PROPAGATION } from "../../../core/signal";
-import { makeDiv } from "../../../core/utils";
+import { makeDiv, safeModulo } from "../../../core/utils";
 import { KEYMAPPINGS } from "../../key_action_mapper";
 import { MetaBuilding } from "../../meta_building";
 import { GameRoot } from "../../root";
@@ -164,11 +164,8 @@ export class HUDBaseToolbar extends BaseHUDPart {
             ? -1
             : 1;
         let newIndex = this.lastSelectedIndex;
-        for (let i = 0; i < this.primaryBuildings.length; ++i, newIndex += direction) {
-            newIndex %= this.primaryBuildings.length;
-            if (newIndex < 0) {
-                newIndex += this.primaryBuildings.length;
-            }
+        for (let i = 0; i < this.primaryBuildings.length; ++i) {
+            newIndex = safeModulo(newIndex + direction, this.primaryBuildings.length);
             const metaBuilding = gMetaBuildingRegistry.findByClass(this.primaryBuildings[newIndex]);
             const handle = this.buildingHandles[metaBuilding.id];
             if (!handle.selected && handle.unlocked) {
diff --git a/src/js/game/hud/parts/building_placer_logic.js b/src/js/game/hud/parts/building_placer_logic.js
index cd189603..986db1b4 100644
--- a/src/js/game/hud/parts/building_placer_logic.js
+++ b/src/js/game/hud/parts/building_placer_logic.js
@@ -3,6 +3,7 @@ import { gMetaBuildingRegistry } from "../../../core/global_registries";
 import { Signal, STOP_PROPAGATION } from "../../../core/signal";
 import { TrackedState } from "../../../core/tracked_state";
 import { Vector } from "../../../core/vector";
+import { safeModulo } from "../../../core/utils";
 import { enumMouseButton } from "../../camera";
 import { StaticMapEntityComponent } from "../../components/static_map_entity";
 import { Entity } from "../../entity";
@@ -471,10 +472,7 @@ export class HUDBuildingPlacerLogic extends BaseHUDPart {
                 .pressed
                 ? -1
                 : 1;
-            let newIndex = (index + direction) % availableVariants.length;
-            if (newIndex < 0) {
-                newIndex += availableVariants.length;
-            }
+            let newIndex = safeModulo(index + direction, availableVariants.length);
             const newVariant = availableVariants[newIndex];
             this.setVariant(newVariant);
         }