diff --git a/lib/uber_task/retry_task.rb b/lib/uber_task/retry_task.rb
index d80efa2..29d927e 100644
--- a/lib/uber_task/retry_task.rb
+++ b/lib/uber_task/retry_task.rb
@@ -7,10 +7,19 @@ class RetryTask < Exception # rubocop:disable Lint/InheritException
     attr_accessor :reason,
                   :wait
 
-    def initialize(reason: nil, wait: nil)
+    def initialize(reason: nil, wait: 0)
+      validate_wait_value!(wait)
+
       super('Requested to retry the task.')
       @reason = reason
       @wait = wait
     end
+
+    private
+
+    def validate_wait_value!(value)
+      raise ArgumentError, '`wait` is not numberic' unless value.is_a?(Numeric)
+      raise ArgumentError, '`wait` cannot be negative' if value.negative?
+    end
   end
 end
diff --git a/spec/uber_task/retry_task_spec.rb b/spec/uber_task/retry_task_spec.rb
index 6feb91f..4e2a945 100644
--- a/spec/uber_task/retry_task_spec.rb
+++ b/spec/uber_task/retry_task_spec.rb
@@ -20,7 +20,25 @@
     expect(exception.wait).to eq(42)
   end
 
+  it 'has 0 as a default wait attribute value' do
+    expect(described_class.new.wait).to eq(0)
+  end
+
   it 'has a message' do
     expect(exception.message).to eq('Requested to retry the task.')
   end
+
+  describe 'wait attribute validations' do
+    it 'does not allow non-numeric value' do
+      expect do
+        described_class.new(wait: 'string')
+      end.to raise_error(ArgumentError, '`wait` is not numberic')
+    end
+
+    it 'does not allow negative value' do
+      expect do
+        described_class.new(wait: -1)
+      end.to raise_error(ArgumentError, '`wait` cannot be negative')
+    end
+  end
 end