diff --git a/packages/toolkit/src/mapBuilders.ts b/packages/toolkit/src/mapBuilders.ts
index 559e234d03..90bbe7d50e 100644
--- a/packages/toolkit/src/mapBuilders.ts
+++ b/packages/toolkit/src/mapBuilders.ts
@@ -140,7 +140,7 @@ export function executeReducerBuilderCallback<S>(
     ) {
       if (process.env.NODE_ENV !== 'production') {
         /*
-         to keep the definition by the user in line with actual behavior, 
+         to keep the definition by the user in line with actual behavior,
          we enforce `addCase` to always be called before calling `addMatcher`
          as matching cases take precedence over matchers
          */
@@ -159,9 +159,14 @@ export function executeReducerBuilderCallback<S>(
         typeof typeOrActionCreator === 'string'
           ? typeOrActionCreator
           : typeOrActionCreator.type
+      if (!type) {
+        throw new Error(
+          '`builder.addCase` cannot be called with an empty action type'
+        )
+      }
       if (type in actionsMap) {
         throw new Error(
-          'addCase cannot be called with two reducers for the same action type'
+          '`builder.addCase` cannot be called with two reducers for the same action type'
         )
       }
       actionsMap[type] = reducer
diff --git a/packages/toolkit/src/tests/createReducer.test.ts b/packages/toolkit/src/tests/createReducer.test.ts
index 5c3a181168..4fb840f696 100644
--- a/packages/toolkit/src/tests/createReducer.test.ts
+++ b/packages/toolkit/src/tests/createReducer.test.ts
@@ -460,7 +460,7 @@ describe('createReducer', () => {
             .addCase(decrement, (state, action) => state - action.payload)
         )
       ).toThrowErrorMatchingInlineSnapshot(
-        `"addCase cannot be called with two reducers for the same action type"`
+        '"`builder.addCase` cannot be called with two reducers for the same action type"'
       )
       expect(() =>
         createReducer(0, (builder) =>
@@ -470,7 +470,25 @@ describe('createReducer', () => {
             .addCase(decrement, (state, action) => state - action.payload)
         )
       ).toThrowErrorMatchingInlineSnapshot(
-        `"addCase cannot be called with two reducers for the same action type"`
+        '"`builder.addCase` cannot be called with two reducers for the same action type"'
+      )
+    })
+
+    test('will throw if an empty type is used', () => {
+      const customActionCreator = (payload: number) => ({
+        type: 'custom_action',
+        payload,
+      })
+      customActionCreator.type = ""
+      expect(() =>
+        createReducer(0, (builder) =>
+          builder.addCase(
+            customActionCreator,
+            (state, action) => state + action.payload
+          )
+        )
+      ).toThrowErrorMatchingInlineSnapshot(
+        '"`builder.addCase` cannot be called with an empty action type"'
       )
     })
   })