diff --git a/qt/org.eclipse.cdt.qt.core/src/org/eclipse/cdt/internal/qt/core/build/QtBuildConfigurationFactory.java b/qt/org.eclipse.cdt.qt.core/src/org/eclipse/cdt/internal/qt/core/build/QtBuildConfigurationFactory.java
index 5467b3d85f7..0faab232710 100644
--- a/qt/org.eclipse.cdt.qt.core/src/org/eclipse/cdt/internal/qt/core/build/QtBuildConfigurationFactory.java
+++ b/qt/org.eclipse.cdt.qt.core/src/org/eclipse/cdt/internal/qt/core/build/QtBuildConfigurationFactory.java
@@ -162,7 +162,7 @@ public class QtBuildConfigurationFactory implements IAdapterFactory {
 					|| event.getType() == IResourceChangeEvent.PRE_DELETE) {
 				if (event.getResource().getType() == IResource.PROJECT) {
 					IProject project = event.getResource().getProject();
-					if (QtNature.hasNature(project)) {
+					if (project.isOpen() && project.exists() && QtNature.hasNature(project)) {
 						try {
 							for (IBuildConfiguration config : project.getBuildConfigs()) {
 								cache.remove(config);