diff --git a/REFERENCE.md b/REFERENCE.md
index 6531cf6c..0678e9c6 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -3065,11 +3065,11 @@ Default value: `undef`
 
 ##### <a name="-docker--run--memory_limit"></a>`memory_limit`
 
-Data type: `Pattern[/^[\d]*(b|k|m|g)$/]`
+Data type: `Optional[Pattern[/^[\d]*(b|k|m|g)$/]]`
 
 
 
-Default value: `'0b'`
+Default value: `undef`
 
 ##### <a name="-docker--run--cpuset"></a>`cpuset`
 
diff --git a/manifests/run.pp b/manifests/run.pp
index 535d6efe..dd5275aa 100644
--- a/manifests/run.pp
+++ b/manifests/run.pp
@@ -21,9 +21,9 @@
 # puppet help.
 #
 # @param verify_digest
-#   (optional) Make sure, that the image has not modified. Compares the digest 
+#   (optional) Make sure, that the image has not modified. Compares the digest
 #   checksum before starting the docker image.
-#   To get the digest of an image, run the following command: 
+#   To get the digest of an image, run the following command:
 #     docker image inspect <<image>> --format='{{index .RepoDigests 0}}
 #
 # @param service_prefix
@@ -196,7 +196,7 @@
   Enum[present,absent]                      $ensure                            = 'present',
   Optional[String]                          $verify_digest                     = undef,
   Optional[String]                          $command                           = undef,
-  Pattern[/^[\d]*(b|k|m|g)$/]               $memory_limit                      = '0b',
+  Optional[Pattern[/^[\d]*(b|k|m|g)$/]]     $memory_limit                      = undef,
   Variant[String,Array,Undef]               $cpuset                            = [],
   Variant[String,Array,Undef]               $ports                             = [],
   Variant[String,Array,Undef]               $labels                            = [],
diff --git a/spec/defines/run_spec.rb b/spec/defines/run_spec.rb
index 4d27df89..aba748bd 100644
--- a/spec/defines/run_spec.rb
+++ b/spec/defines/run_spec.rb
@@ -288,7 +288,7 @@
             'links' => [],
             'lxc_conf' => [],
             'manage_service' => true,
-            'memory_limit' => '0b',
+            'memory_limit' => :undef,
             'net' => 'bridge',
             'ports' => [],
             'privileged' => false,