diff --git a/src/engine.js b/src/engine.js
index 2a0ee48..178bc83 100644
--- a/src/engine.js
+++ b/src/engine.js
@@ -66,6 +66,7 @@ class Engine extends EventEmitter {
 
     let index = this.rules.indexOf(rule)
     if (index === -1) return false
+    this.prioritizedRules = null
     return Boolean(this.rules.splice(index, 1).length)
   }
 
diff --git a/test/engine.test.js b/test/engine.test.js
index f72c451..f5b48cb 100644
--- a/test/engine.test.js
+++ b/test/engine.test.js
@@ -89,6 +89,7 @@ describe('Engine', () => {
         expect(engine.rules.length).to.equal(1)
         engine.removeRule(rule)
         expect(engine.rules.length).to.equal(0)
+        expect(engine.prioritizedRules).to.equal(null)
       })
     })
 
@@ -106,6 +107,14 @@ describe('Engine', () => {
       const isRemoved = engine.removeRule(rule)
       expect(isRemoved).to.equal(false)
     })
+
+    it('clears the "prioritizedRules" cache', () => {
+      let rule = new Rule(factories.rule())
+      engine.addRule(rule)
+      engine.prioritizeRules()
+      engine.removeRule(rule)
+      expect(engine.prioritizedRules).to.equal(null)
+    })
   })
 
   describe('addOperator()', () => {