diff --git a/Aspects.m b/Aspects.m
index c907066..612fd36 100644
--- a/Aspects.m
+++ b/Aspects.m
@@ -45,7 +45,7 @@ - (id)initWithInstance:(__unsafe_unretained id)instance invocation:(NSInvocation
 @end
 
 // Tracks a single aspect.
-@interface AspectIdentifier : NSObject
+@interface AspectIdentifier : NSObject <AspectToken>
 + (instancetype)identifierWithSelector:(SEL)selector object:(id)object options:(AspectOptions)options block:(id)block error:(NSError **)error;
 - (BOOL)invokeWithInfo:(id<AspectInfo>)info;
 @property (nonatomic, assign) SEL selector;