diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/index/IndexLocationFactory.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/index/IndexLocationFactory.java
index 24ee1579219..5c21dca6af7 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/index/IndexLocationFactory.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/index/IndexLocationFactory.java
@@ -7,18 +7,24 @@
  *
  * Contributors:
  *    Andrew Ferguson (Symbian) - initial API and implementation
+ *    Markus Schorn (Wind River Systems)
  *******************************************************************************/ 
 package org.eclipse.cdt.core.index;
 
 import java.net.URI;
+import java.util.Arrays;
+import java.util.Comparator;
 
+import org.eclipse.cdt.core.CProjectNature;
 import org.eclipse.cdt.core.model.ICProject;
 import org.eclipse.cdt.core.model.ITranslationUnit;
 import org.eclipse.cdt.internal.core.index.IndexFileLocation;
 import org.eclipse.core.filesystem.URIUtil;
 import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.Path;
 
@@ -35,6 +41,25 @@ import org.eclipse.core.runtime.Path;
  * @since 4.0
  */
 public class IndexLocationFactory {
+	/**
+	 * Comparator to sort files for location.
+	 */
+	private static final class FILE_COMPARATOR implements Comparator<IFile> {
+		public int compare(IFile o1, IFile o2) {
+			return compare(o1.getLocationURI(), o2.getLocationURI());
+		}
+
+		private int compare(URI uri1, URI uri2) {
+			if (uri1 == uri2)
+				return 0;
+			if (uri1 == null)
+				return -1;
+			if (uri2 == null)
+				return 1;
+			return uri1.toString().compareTo(uri2.toString());
+		}
+	}
+
 	/**
 	 * Returns
 	 * <ul>
@@ -89,16 +114,36 @@ public class IndexLocationFactory {
 	 */
 	public static IIndexFileLocation getIFLExpensive(ICProject cproject, String absolutePath) {
 		IFile[] files = ResourcesPlugin.getWorkspace().getRoot().findFilesForLocation(new Path(absolutePath));
-		if(files.length==1) {
+		switch(files.length) {
+		case 0:
+			return getExternalIFL(absolutePath);
+		case 1:
 			return getWorkspaceIFL(files[0]);
 		}
-		if(cproject!=null) {
-			for(int i=0; i<files.length; i++) {
-				if(files[i].getProject().equals(cproject.getProject()))
-					return getWorkspaceIFL(files[i]);
+		
+		Arrays.sort(files, new FILE_COMPARATOR());
+		final IProject preferredProject= cproject == null ? null : cproject.getProject();
+		IFile fileInCProject= null;
+		for (IFile file : files) {
+			// check for preferred project
+			final IProject project = file.getProject();
+			if (preferredProject != null && preferredProject.equals(project)) 
+				return getWorkspaceIFL(file);
+			
+			if (fileInCProject == null) {
+				try {
+					if (project.hasNature(CProjectNature.C_NATURE_ID)) {
+						fileInCProject= file;
+					}
+				} catch (CoreException e) {
+					// treat as non-c project
+				}
 			}
 		}
-		return new IndexFileLocation(URIUtil.toURI(absolutePath), null);
+		if (fileInCProject != null) 
+			return getWorkspaceIFL(fileInCProject);
+		
+		return getWorkspaceIFL(files[0]);
 	}
 	
 	/**