diff --git a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/GnuMakefileGenerator.java b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/GnuMakefileGenerator.java
index 0630d1eb4e7..09c975a22ad 100644
--- a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/GnuMakefileGenerator.java
+++ b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/makegen/gnu/GnuMakefileGenerator.java
@@ -524,9 +524,10 @@ public class GnuMakefileGenerator implements IManagedBuilderMakefileGenerator {
 				if (info.buildsFileType(ext)) {
  					// look for the extension in the map
  					StringBuffer bufferForExtension = new StringBuffer();
- 					if (extensionToRuleStringMap.containsKey(ext)) {
- 						bufferForExtension.append(extensionToRuleStringMap.get(ext).toString());
+ 					if (!extensionToRuleStringMap.containsKey(ext)) {
+ 						continue;
  					}
+ 					bufferForExtension.append(extensionToRuleStringMap.get(ext).toString());
  					if(bufferForExtension != null &&
  							!getOutputExtensions().contains(bufferForExtension.toString())) {