diff --git a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/internal/core/Tool.java b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/internal/core/Tool.java
index b7ebec459bd..1edd1c1c93b 100644
--- a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/internal/core/Tool.java
+++ b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/internal/core/Tool.java
@@ -2476,6 +2476,10 @@ public class Tool extends HoldsOptions implements ITool, IOptionCategory, IMatch
 	}
 	
 	private void setOutputPrefixForType(IOutputType type, String prefix){
+		if(prefix == null){
+			if(type.getParent() != this)
+				return;
+		}
 		type = getEdtableOutputType(type);
 		type.setOutputPrefix(prefix);
 		setRebuildState(true);