diff --git a/Makefile b/Makefile
index 3fc227d2ba621934d41e6533caa75a555a132c5f..a65019da4ca5c65e5d482084bb7a35a08062b79d 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ BASE=rules_shipping
 BASE_ADV=rules_shipping_advanced
 PLUGINTYPE=vmshipment
 ZIPBASE=opentools_vm
-VERSION=5.5
+VERSION=5.6
 
 PLUGINFILES=$(BASE).php $(BASE)_base.php $(BASE).script.php $(BASE).xml index.html
 PLUGINFILES_ADV=$(BASE_ADV).php $(BASE)_base.php $(BASE_ADV).script.php $(BASE_ADV).xml index.html
diff --git a/releases/plg_opentools_vm_rules_shipping_advanced_v5.6.zip b/releases/plg_opentools_vm_rules_shipping_advanced_v5.6.zip
new file mode 100644
index 0000000000000000000000000000000000000000..59280c5b0dd9a5ca8ac3ab71213fc37b53cae8d9
Binary files /dev/null and b/releases/plg_opentools_vm_rules_shipping_advanced_v5.6.zip differ
diff --git a/releases/plg_opentools_vm_rules_shipping_v5.6.zip b/releases/plg_opentools_vm_rules_shipping_v5.6.zip
new file mode 100644
index 0000000000000000000000000000000000000000..6c43ad24a2bf8ab9f05ab2d08e24099d42cc248c
Binary files /dev/null and b/releases/plg_opentools_vm_rules_shipping_v5.6.zip differ
diff --git a/rules_shipping.xml b/rules_shipping.xml
index 090c13c9eb4a1eadc5308549f4ff066a5a270af0..2f691c73da0d3d687b443e74aab63bec70a23d12 100644
--- a/rules_shipping.xml
+++ b/rules_shipping.xml
@@ -6,7 +6,7 @@
     <authorUrl>http://www.open-tools.net</authorUrl>
     <copyright>Copyright (C) 2013-2014, Reinhold Kainhofer</copyright>
     <license>GPL v3+</license>
-    <version>5.5</version>
+    <version>5.6</version>
     <description>VMSHIPMENT_RULES_DESC</description>
     <files>
         <filename plugin="rules_shipping">rules_shipping.php</filename>
diff --git a/rules_shipping_advanced.xml b/rules_shipping_advanced.xml
index bcb7831bd6973cc68870a57e3f078adf49b57d8f..58b42e4bfd582ff88c1476e8c39804d55d7f13cb 100644
--- a/rules_shipping_advanced.xml
+++ b/rules_shipping_advanced.xml
@@ -6,7 +6,7 @@
     <authorUrl>http://www.open-tools.net</authorUrl>
     <copyright>Copyright (C) 2013-2014, Reinhold Kainhofer</copyright>
     <license>GPL v3+</license>
-    <version>5.5</version>
+    <version>5.6</version>
     <description>VMSHIPMENT_RULES_ADV_DESC</description>
     <files>
         <filename plugin="rules_shipping_advanced">rules_shipping_advanced.php</filename>
diff --git a/rules_shipping_base.php b/rules_shipping_base.php
index d5db222380618baa61cd15757a377b2c50dbdb2c..f250d03151baf60c0e9434115887970df857892e 100644
--- a/rules_shipping_base.php
+++ b/rules_shipping_base.php
@@ -1045,7 +1045,7 @@ class ShippingRule {
 		/* In the advanced version, all conditions and costs can be given as a full mathematical expression */
 		/* Both versions create an expression tree, which can be easily evaluated in evaluateTerm */
 		$rulepart = trim($rulepart);
-		if (empty($rulepart)) return;
+		if (!isset($rulepart) || $rulepart==='') return;
 
 		
 		// Special-case the name assignment, where we don't want to interpret the value as an arithmetic expression!
@@ -1056,7 +1056,6 @@ class ShippingRule {
 
 		// Split at all operators:
 		$atoms = $this->tokenize_expression ($rulepart);
-		
 		/* TODO: Starting from here, the advanced plugin is different! */
 		$operators = array('<', '<=', '=', '>', '>=', '=>', '=<', '<>', '!=', '==');
 		if (count($atoms)==1) {