diff --git a/application/forms/IcingaDependencyForm.php b/application/forms/IcingaDependencyForm.php
index dedbc634..b2cb94ec 100644
--- a/application/forms/IcingaDependencyForm.php
+++ b/application/forms/IcingaDependencyForm.php
@@ -113,7 +113,10 @@ class IcingaDependencyForm extends DirectorObjectForm
             'required' => true,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaHostGroupForm.php b/application/forms/IcingaHostGroupForm.php
index 9cdb3b92..be48318e 100644
--- a/application/forms/IcingaHostGroupForm.php
+++ b/application/forms/IcingaHostGroupForm.php
@@ -28,7 +28,10 @@ class IcingaHostGroupForm extends DirectorObjectForm
             'required' => false,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaNotificationForm.php b/application/forms/IcingaNotificationForm.php
index f3bc56cb..3b657f64 100644
--- a/application/forms/IcingaNotificationForm.php
+++ b/application/forms/IcingaNotificationForm.php
@@ -104,7 +104,10 @@ class IcingaNotificationForm extends DirectorObjectForm
             'suggestionContext' => $suggestionContext,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaScheduledDowntimeForm.php b/application/forms/IcingaScheduledDowntimeForm.php
index d7c83162..2b929ff5 100644
--- a/application/forms/IcingaScheduledDowntimeForm.php
+++ b/application/forms/IcingaScheduledDowntimeForm.php
@@ -109,7 +109,10 @@ class IcingaScheduledDowntimeForm extends DirectorObjectForm
             'required' => true,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaServiceForm.php b/application/forms/IcingaServiceForm.php
index b6d825fb..b9e573ee 100644
--- a/application/forms/IcingaServiceForm.php
+++ b/application/forms/IcingaServiceForm.php
@@ -446,7 +446,10 @@ class IcingaServiceForm extends DirectorObjectForm
             'required' => true,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaServiceGroupForm.php b/application/forms/IcingaServiceGroupForm.php
index 65b8dfeb..db23cbbb 100644
--- a/application/forms/IcingaServiceGroupForm.php
+++ b/application/forms/IcingaServiceGroupForm.php
@@ -28,7 +28,10 @@ class IcingaServiceGroupForm extends DirectorObjectForm
             'required' => false,
             'description' => $this->translate(
                 'This allows you to configure an assignment filter. Please feel'
-                . ' free to combine as many nested operators as you want'
+                . ' free to combine as many nested operators as you want. The'
+                . ' "contains" operator is valid for arrays only. Please use'
+                . ' wildcards and the = (equals) operator when searching for'
+                . ' partial string matches, like in *.example.com'
             )
         ]);
 
diff --git a/application/forms/IcingaServiceSetForm.php b/application/forms/IcingaServiceSetForm.php
index 775eea9b..d4841a1b 100644
--- a/application/forms/IcingaServiceSetForm.php
+++ b/application/forms/IcingaServiceSetForm.php
@@ -121,7 +121,10 @@ class IcingaServiceSetForm extends DirectorObjectForm
                 'This allows you to configure an assignment filter. Please feel'
                 . ' free to combine as many nested operators as you want. You'
                 . ' might also want to skip this, define it later and/or just'
-                . ' add this set of services to single hosts'
+                . ' add this set of services to single hosts. The "contains"'
+                . ' operator is valid for arrays only. Please use wildcards and'
+                . ' the = (equals) operator when searching for partial string'
+                . ' matches, like in *.example.com'
             )
         ]);