diff --git a/manifests/service_validation.pp b/manifests/service_validation.pp
index 8a9ccd05..93905fba 100644
--- a/manifests/service_validation.pp
+++ b/manifests/service_validation.pp
@@ -45,6 +45,14 @@
 # Number of seconds between validation attempts;
 # string; optional; default to '2'
 #
+# [*onlyif*]
+# Run the exec if all conditions in the array return true.
+# string or array; optional; default to 'undef'
+#
+# [*unless*]
+# Run the exec if all conditions in the array return false.
+# string or array; optional; default to 'undef'
+#
 define openstacklib::service_validation(
   $command,
   $service_name = $name,
@@ -52,14 +60,22 @@ define openstacklib::service_validation(
   $provider     = shell,
   $tries        = '10',
   $try_sleep    = '2',
+  $onlyif       = undef,
+  $unless       = undef,
 ) {
 
+  if $onlyif and $unless {
+    fail ('Only one parameter should be declared: onlyif or unless')
+  }
+
   exec { "execute ${service_name} validation":
     path      => $path,
     provider  => $provider,
     command   => $command,
     tries     => $tries,
     try_sleep => $try_sleep,
+    onlyif    => $onlyif,
+    unless    => $unless,
   }
 
   anchor { "create ${service_name} anchor":
@@ -67,3 +83,4 @@ define openstacklib::service_validation(
   }
 
 }
+
diff --git a/spec/defines/openstacklib_service_validation_spec.rb b/spec/defines/openstacklib_service_validation_spec.rb
index cc196f07..1d1b4067 100644
--- a/spec/defines/openstacklib_service_validation_spec.rb
+++ b/spec/defines/openstacklib_service_validation_spec.rb
@@ -46,6 +46,46 @@ describe 'openstacklib::service_validation' do
 
     end
 
+    context 'with unless parameter' do
+      let :params do
+        required_params.merge!({ :unless  => 'pwd' })
+      end
+
+      it { is_expected.to contain_exec("execute #{title} validation").with(
+        :path      => '/usr/bin:/bin:/usr/sbin:/sbin',
+        :provider  => 'shell',
+        :command   => 'nova list',
+        :tries     => '10',
+        :try_sleep => '2',
+        :unless    => 'pwd',
+      )}
+
+      it { is_expected.to contain_anchor("create #{title} anchor").with(
+        :require => "Exec[execute #{title} validation]",
+      )}
+
+    end
+
+    context 'with onlyif parameter' do
+      let :params do
+        required_params.merge!({:onlyif  => 'pwd' })
+      end
+
+      it { is_expected.to contain_exec("execute #{title} validation").with(
+        :path      => '/usr/bin:/bin:/usr/sbin:/sbin',
+        :provider  => 'shell',
+        :command   => 'nova list',
+        :tries     => '10',
+        :try_sleep => '2',
+        :onlyif    => 'pwd',
+      )}
+
+      it { is_expected.to contain_anchor("create #{title} anchor").with(
+        :require => "Exec[execute #{title} validation]",
+      )}
+
+    end
+
     context 'when omitting a required parameter command' do
       let :params do
         required_params.delete(:command)