diff --git a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/language/settings/providers/AbstractBuiltinSpecsDetector.java b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/language/settings/providers/AbstractBuiltinSpecsDetector.java
index 1a88534c671..fea69686a9e 100644
--- a/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/language/settings/providers/AbstractBuiltinSpecsDetector.java
+++ b/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/language/settings/providers/AbstractBuiltinSpecsDetector.java
@@ -42,7 +42,6 @@ import org.eclipse.cdt.managedbuilder.core.ManagedBuilderCorePlugin;
 import org.eclipse.cdt.managedbuilder.internal.core.ManagedMakeMessages;
 import org.eclipse.cdt.utils.CommandLineUtil;
 import org.eclipse.core.resources.IMarker;
-import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.IWorkspaceRoot;
 import org.eclipse.core.resources.ResourcesPlugin;
@@ -381,14 +380,17 @@ public abstract class AbstractBuiltinSpecsDetector extends AbstractLanguageSetti
 			}
 		};
 
-		IProject project = null;
+		ISchedulingRule rule = null;
 		if (currentCfgDescription != null) {
 			ICProjectDescription prjDescription = currentCfgDescription.getProjectDescription();
 			if (prjDescription != null) {
-				project = prjDescription.getProject();
+				rule = prjDescription.getProject();
 			}
 		}
-		job.setRule(project);
+		if (rule == null) {
+			rule = ResourcesPlugin.getWorkspace().getRoot();
+		}
+		job.setRule(rule);
 		job.schedule();
 
 		// AG FIXME - temporary log to remove before CDT Juno release
diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/language/settings/providers/LanguageSettingsProvidersSerializer.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/language/settings/providers/LanguageSettingsProvidersSerializer.java
index 997982888df..b4f86bded17 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/language/settings/providers/LanguageSettingsProvidersSerializer.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/language/settings/providers/LanguageSettingsProvidersSerializer.java
@@ -47,6 +47,7 @@ import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.IWorkspaceRoot;
 import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.resources.WorkspaceJob;
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
@@ -565,9 +566,9 @@ public class LanguageSettingsProvidersSerializer {
 			}
 		}
 
-		Job job = new Job(SettingsModelMessages.getString("LanguageSettingsProvidersSerializer.SerializeJobName")) { //$NON-NLS-1$
+		Job job = new WorkspaceJob(SettingsModelMessages.getString("LanguageSettingsProvidersSerializer.SerializeJobName")) { //$NON-NLS-1$
 			@Override
-			protected IStatus run(IProgressMonitor monitor) {
+			public IStatus runInWorkspace(IProgressMonitor monitor) throws CoreException {
 				try {
 					monitor.beginTask(SettingsModelMessages.getString("LanguageSettingsProvidersSerializer.SerializingForWorkspace"), //$NON-NLS-1$
 							TICKS_SERIALIZING);
@@ -587,7 +588,6 @@ public class LanguageSettingsProvidersSerializer {
 			}
 		};
 
-		job.setRule(null);
 		job.schedule();
 	}