diff --git a/plugins/org.eclipse.emf.henshin.interpreter/src/org/eclipse/emf/henshin/interpreter/impl/EngineImpl.java b/plugins/org.eclipse.emf.henshin.interpreter/src/org/eclipse/emf/henshin/interpreter/impl/EngineImpl.java
index 5fb276b..3c610c6 100644
--- a/plugins/org.eclipse.emf.henshin.interpreter/src/org/eclipse/emf/henshin/interpreter/impl/EngineImpl.java
+++ b/plugins/org.eclipse.emf.henshin.interpreter/src/org/eclipse/emf/henshin/interpreter/impl/EngineImpl.java
@@ -762,9 +762,14 @@
 		RuleChangeInfo ruleChange = getRuleInfo(rule).getChangeInfo();
 		List<Change> changes= complexChange.getChanges();
 
+		// Set parameters:
 		for (Parameter param : rule.getParameters()) {
 			Object value = completeMatch.getParameterValue(param);
-			resultMatch.setParameterValue(param, value);
+			if (value != null) {
+				resultMatch.setParameterValue(param, value);
+			} else {
+				value = resultMatch.getParameterValue(param);
+			}
 			scriptEngine.getEngine().put(param.getName(), value);
 		}