Index: modules/core/src/main/java/org/jbpm/graph/node/ProcessState.java
===================================================================
--- modules/core/src/main/java/org/jbpm/graph/node/ProcessState.java	(revision 15852)
+++ modules/core/src/main/java/org/jbpm/graph/node/ProcessState.java	(working copy)
@@ -197,7 +197,7 @@
           Object value = superContextInstance.getVariable(variableName, superProcessToken);
           String mappedName = variableAccess.getMappedName();
           log.debug("copying super process var '" + variableName + "' to sub process var '" + mappedName + "': " + value);
-          if (value != null)
+          //if (value != null)
           {
             subContextInstance.setVariable(mappedName, value);
           }
@@ -234,7 +234,7 @@
           Object value = subContextInstance.getVariable(mappedName);
           String variableName = variableAccess.getVariableName();
           log.debug("copying sub process var '" + mappedName + "' to super process var '" + variableName + "': " + value);
-          if (value != null)
+          //if (value != null)
           {
             superContextInstance.setVariable(variableName, value, superProcessToken);
           }