diff --git a/README.md b/README.md
index 4246ea5..31fdce2 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,7 @@ Currently state supports the following options:
 
   - `initial` : `Bool` **optional** - indicates whether this state is initial or not. If initial state not specified, first one will be considered as initial
   - `guard` : `(-> Bool)` **optional** - a callback, that gets evaluated once state is getting entered. State will not enter if guard returns false
-  - `enter` : `(-> Nil)` **optional** - a hook, that gets evaluated once state entered.
+  - `enter` : `(->)` **optional** - a hook, that gets evaluated once state entered.
 
 ### Events
 
diff --git a/spec/aasm/state_machine_spec.cr b/spec/aasm/state_machine_spec.cr
index f1a8b07..e6338bd 100644
--- a/spec/aasm/state_machine_spec.cr
+++ b/spec/aasm/state_machine_spec.cr
@@ -140,21 +140,21 @@ module AASM
 
       it "runs enter block" do
         count = 0
-        s = two_states_machine enter: ->{ count += 1; nil }
+        s = two_states_machine enter: ->{ count += 1 }
         s.fire_event :activate
         count.should eq 1
       end
 
       it "does not run enter block if guard returns false" do
         count = 0
-        s = two_states_machine enter: ->{ count += 1; nil }, guard: ->{ false }
+        s = two_states_machine enter: ->{ count += 1 }, guard: ->{ false }
         s.fire_event :activate
         count.should eq 0
       end
 
       it "should not run block twice if event gets fired twice" do
         count = 0
-        s = two_states_machine enter: ->{ count += 1; nil }
+        s = two_states_machine enter: ->{ count += 1 }
         s.fire_event :activate
         s.fire_event :activate
         count.should eq 1
@@ -162,7 +162,7 @@ module AASM
 
       it "should handle cycled states" do
         count = 0
-        s = one_state_machine enter: ->{ count += 1; nil }
+        s = one_state_machine enter: ->{ count += 1 }
         s.fire_event :restart
         s.current_state_name.should eq :started
         count.should eq 1
diff --git a/spec/aasm/state_spec.cr b/spec/aasm/state_spec.cr
index 79da9f8..7dd7f1b 100644
--- a/spec/aasm/state_spec.cr
+++ b/spec/aasm/state_spec.cr
@@ -14,6 +14,11 @@ module AASM
         t.enter.should_not be_nil
       end
 
+      it "accepts :enter that can return anything" do
+        t = State.new({enter: ->{ "anything" }})
+        t.enter.not_nil!.call.should be_nil
+      end
+
       it "accepts :guard" do
         t = State.new({guard: ->{ true }})
         t.guard.should_not be_nil
diff --git a/spec/aasm_spec.cr b/spec/aasm_spec.cr
index bc57b86..5a94f9d 100644
--- a/spec/aasm_spec.cr
+++ b/spec/aasm_spec.cr
@@ -10,7 +10,7 @@ class Transaction
 
   def act_as_state_machine
     aasm.state :pending, initial: true
-    aasm.state :active, enter: ->{ @count += 1; nil }
+    aasm.state :active, enter: ->{ @count += 1 }
     aasm.state :completed
 
     aasm.event :activate do |e|
diff --git a/src/aasm/state.cr b/src/aasm/state.cr
index 19fc6ce..2af3559 100644
--- a/src/aasm/state.cr
+++ b/src/aasm/state.cr
@@ -3,7 +3,9 @@ struct AASM::State
   getter guard : (-> Bool)?
 
   def initialize(opts = {enter: nil, guard: nil})
-    @enter = opts[:enter]?
+    if enter = opts[:enter]?
+      @enter = -> { enter.not_nil!.call; nil }
+    end
     @guard = opts[:guard]?
   end
 end
diff --git a/src/aasm/state_machine.cr b/src/aasm/state_machine.cr
index f7aea29..1ddb084 100644
--- a/src/aasm/state_machine.cr
+++ b/src/aasm/state_machine.cr
@@ -7,7 +7,7 @@ class AASM::StateMachine
     @transition_table = {} of Symbol => Array(Symbol)
   end
 
-  def state(name : Symbol, initial : Bool = false, enter : (-> Nil) = nil, guard : (-> Bool) = nil)
+  def state(name : Symbol, initial : Bool = false, enter : (-> _) = nil, guard : (-> Bool) = nil)
     check_states_already_defined name
     state = State.new({enter: enter, guard: guard})
     @current_state_name = name if initial || @current_state_name.nil?