diff --git a/lib/shoryuken/manager.rb b/lib/shoryuken/manager.rb
index ad940a02..f954f04c 100644
--- a/lib/shoryuken/manager.rb
+++ b/lib/shoryuken/manager.rb
@@ -11,7 +11,8 @@ class Manager
     trap_exit :processor_died
 
     def initialize(condvar)
-      @count  = Shoryuken.options[:concurrency] || 25
+      @count = Shoryuken.options[:concurrency] || 25
+      raise(ArgumentError, "Concurrency value #{@count} is invalid, it needs to be a positive number") unless @count > 0
       @queues = Shoryuken.queues.dup.uniq
       @finished = condvar
 
diff --git a/spec/shoryuken/manager_spec.rb b/spec/shoryuken/manager_spec.rb
index c58d0741..0ef0b6ba 100644
--- a/spec/shoryuken/manager_spec.rb
+++ b/spec/shoryuken/manager_spec.rb
@@ -1,13 +1,22 @@
 require 'spec_helper'
 require 'shoryuken/manager'
 
-describe Shoryuken::Manager do
+RSpec.describe Shoryuken::Manager do
   subject do
     condvar = double(:condvar)
     allow(condvar).to receive(:signal).and_return(nil)
     Shoryuken::Manager.new(condvar)
   end
 
+  describe 'Invalid concurrency setting' do
+    it 'raises ArgumentError if concurrency is not positive number' do
+      Shoryuken.options[:concurrency] = -1
+      expect { Shoryuken::Manager.new(nil) }
+        .to raise_error(ArgumentError, 'Concurrency value -1 is invalid, it needs to be a positive number')
+    end
+
+  end
+
   describe 'Auto Scaling' do
     it 'decreases weight' do
       queue1 = 'shoryuken'