diff --git a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/ManagedBuildGnuToolInfo.java b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/ManagedBuildGnuToolInfo.java
index c8d90713952..d2b58fd7c31 100644
--- a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/ManagedBuildGnuToolInfo.java
+++ b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/ManagedBuildGnuToolInfo.java
@@ -624,7 +624,7 @@ public class ManagedBuildGnuToolInfo implements IManagedBuildGnuToolInfo {
 							currList.addAll(Arrays.asList(outNames));
 							myOutputMacros.put(variable, currList);
 						} else {
-							myOutputMacros.put(variable, Arrays.asList(outNames));
+							myOutputMacros.put(variable, new ArrayList(Arrays.asList(outNames)));
 						}
 					}
 				} else