diff --git a/REFERENCE.md b/REFERENCE.md
index 21c7feb9..14988442 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -2888,7 +2888,7 @@ Struct[{
     Optional['MemoryHigh']                => Systemd::Unit::AmountOrPercent,
     Optional['MemoryMax']                 => Systemd::Unit::AmountOrPercent,
     Optional['MemoryLimit']               => Systemd::Unit::Amount,
-    Optional['MemorySwapMax']             => Systemd::Unit::Amount,
+    Optional['MemorySwapMax']             => Systemd::Unit::AmountOrPercent,
     Optional['TasksAccounting']           => Boolean,
     Optional['TasksMax']                  => Systemd::Unit::AmountOrPercent,
     Optional['IOAccounting']              => Boolean,
diff --git a/spec/type_aliases/systemd_unit_service_spec.rb b/spec/type_aliases/systemd_unit_service_spec.rb
index fa31128e..971ed3cc 100644
--- a/spec/type_aliases/systemd_unit_service_spec.rb
+++ b/spec/type_aliases/systemd_unit_service_spec.rb
@@ -103,6 +103,8 @@
     )
   }
 
+  it { is_expected.to allow_value({ 'MemorySwapMax' => '80%' }) }
+
   it { is_expected.not_to allow_value({ 'CPUQuota' => 50 }) }
   it { is_expected.not_to allow_value({ 'CPUQuota' => '0%' }) }
   it { is_expected.not_to allow_value({ 'MemoryHigh' => '1Y' }) }
diff --git a/types/unit/service.pp b/types/unit/service.pp
index 9a24f198..b6bb83c1 100644
--- a/types/unit/service.pp
+++ b/types/unit/service.pp
@@ -57,7 +57,7 @@
     Optional['MemoryHigh']                => Systemd::Unit::AmountOrPercent,
     Optional['MemoryMax']                 => Systemd::Unit::AmountOrPercent,
     Optional['MemoryLimit']               => Systemd::Unit::Amount,
-    Optional['MemorySwapMax']             => Systemd::Unit::Amount,
+    Optional['MemorySwapMax']             => Systemd::Unit::AmountOrPercent,
     Optional['TasksAccounting']           => Boolean,
     Optional['TasksMax']                  => Systemd::Unit::AmountOrPercent,
     Optional['IOAccounting']              => Boolean,