diff --git a/lib/concurrent-ruby/concurrent/executor/serialized_execution.rb b/lib/concurrent-ruby/concurrent/executor/serialized_execution.rb
index 4db7c7f0c..c496afee6 100644
--- a/lib/concurrent-ruby/concurrent/executor/serialized_execution.rb
+++ b/lib/concurrent-ruby/concurrent/executor/serialized_execution.rb
@@ -32,6 +32,8 @@ def call
     #
     # @raise [ArgumentError] if no task is given
     def post(executor, *args, &task)
+      raise ArgumentError.new('no block given') unless block_given?
+
       posts [[executor, args, task]]
       true
     end
diff --git a/spec/concurrent/executor/serialized_execution_spec.rb b/spec/concurrent/executor/serialized_execution_spec.rb
index 11b9bc72c..efe605f15 100644
--- a/spec/concurrent/executor/serialized_execution_spec.rb
+++ b/spec/concurrent/executor/serialized_execution_spec.rb
@@ -4,6 +4,15 @@
 
 module Concurrent
 
+  RSpec.describe SerializedExecution do
+
+    it 'raises an exception when no block is given' do
+      expect {
+        subject.post(ImmediateExecutor.new)
+      }.to raise_error(ArgumentError, 'no block given')
+    end
+  end
+
   RSpec.describe SerializedExecutionDelegator do
 
     subject { SerializedExecutionDelegator.new(ImmediateExecutor.new) }