diff --git a/src/game-logic/reducers/processLevelUp.js b/src/game-logic/reducers/processLevelUp.js
index be83b6664..169a5476f 100644
--- a/src/game-logic/reducers/processLevelUp.js
+++ b/src/game-logic/reducers/processLevelUp.js
@@ -37,7 +37,7 @@ export const processLevelUp = (state, oldLevel) => {
         true
       )
     } else if (levelObject?.unlocksTool) {
-      state.toolLevels = unlockTool(state.toolLevels, levelObject.unlocksTool)
+      state = unlockTool(state, levelObject.unlocksTool)
     } else if (levelObject?.unlocksStageFocusType) {
       state = unlockStage(state, levelObject.unlocksStageFocusType)
     }
diff --git a/src/utils/index.js b/src/utils/index.js
index 54645d39e..f3e5aee50 100644
--- a/src/utils/index.js
+++ b/src/utils/index.js
@@ -974,14 +974,20 @@ export const computeMarketPositions = (
  * @param {farmhand.toolType} toolType
  * @returns {farmhand.state}
  */
-export const unlockTool = (currentToolLevels, toolType) => {
+export const unlockTool = (state, toolType) => {
+  const { currentToolLevels } = state
+
   if (currentToolLevels[toolType] === toolLevel.UNAVAILABLE) {
-    return Object.assign({}, currentToolLevels, {
-      [toolType]: toolLevel.DEFAULT,
-    })
+    return {
+      ...state,
+      currentToolLevels: {
+        ...currentToolLevels,
+        [toolType]: toolLevel.DEFAULT,
+      },
+    }
   }
 
-  return currentToolLevels
+  return state
 }
 
 /*
diff --git a/src/utils/index.test.js b/src/utils/index.test.js
index 446fd48a1..367ae038e 100644
--- a/src/utils/index.test.js
+++ b/src/utils/index.test.js
@@ -1087,12 +1087,34 @@ describe('getGrowingPhase', () => {
 
 describe('unlockTool', () => {
   it('unlocks the specified tool', () => {
-    const tools = {
-      [toolType.SHOVEL]: toolLevel.UNAVAILABLE,
+    const state = {
+      currentToolLevels: {
+        [toolType.SHOVEL]: toolLevel.UNAVAILABLE,
+      },
+    }
+
+    const { currentToolLevels } = unlockTool(state, toolType.SHOVEL)
+
+    expect(currentToolLevels[toolType.SHOVEL]).toEqual(toolLevel.DEFAULT)
+  })
+
+  it('does not alter the rest of the tools', () => {
+    const state = {
+      currentToolLevels: {
+        [toolType.SHOVEL]: toolLevel.UNAVAILABLE,
+        [toolType.HOE]: toolLevel.DEFAULT,
+        [toolType.SCYTHE]: toolLevel.GOLD,
+      },
     }
 
-    const updatedTools = unlockTool(tools, toolType.SHOVEL)
+    const { currentToolLevels } = unlockTool(state, toolType.SHOVEL)
 
-    expect(updatedTools[toolType.SHOVEL]).toEqual(toolLevel.DEFAULT)
+    expect(currentToolLevels).toMatchInlineSnapshot(`
+      Object {
+        "HOE": "DEFAULT",
+        "SCYTHE": "GOLD",
+        "SHOVEL": "DEFAULT",
+      }
+    `)
   })
 })