diff --git a/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectImpl.java b/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectImpl.java
index b3ef2cde5778..9de443ba76ea 100644
--- a/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectImpl.java
@@ -76,6 +76,7 @@ public class ProjectImpl extends PlatformComponentManagerImpl implements Project
   public boolean myOptimiseTestLoadSpeed;
   private String myName;
   private String myOldName;
+  private final boolean myLight;
 
   protected ProjectImpl(@NotNull ProjectManager projectManager,
                         @NotNull String filePath,
@@ -98,6 +99,9 @@ public class ProjectImpl extends PlatformComponentManagerImpl implements Project
     if (!isDefault() && projectName != null && getStateStore().getStorageScheme().equals(StorageScheme.DIRECTORY_BASED)) {
       myOldName = "";  // new project
     }
+    
+    // light project may be changed later during test, so we need to remember its initial state 
+    myLight = ApplicationManager.getApplication().isUnitTestMode() && filePath.contains("light_temp_");
   }
 
   @Override
@@ -105,6 +109,10 @@ public class ProjectImpl extends PlatformComponentManagerImpl implements Project
     return super.isDisposed() || temporarilyDisposed;
   }
 
+  public boolean isLight() {
+    return myLight;
+  }
+
   private volatile boolean temporarilyDisposed;
   @TestOnly
   public void setTemporarilyDisposed(boolean disposed) {
diff --git a/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectManagerImpl.java b/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectManagerImpl.java
index c68ec93bd415..498cd5bfa3d4 100644
--- a/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectManagerImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/project/impl/ProjectManagerImpl.java
@@ -862,7 +862,7 @@ public class ProjectManagerImpl extends ProjectManagerEx implements PersistentSt
 
   @TestOnly
   public static boolean isLight(@NotNull Project project) {
-    return ApplicationManager.getApplication().isUnitTestMode() && project.toString().contains("light_temp_");
+    return project instanceof ProjectImpl && ((ProjectImpl)project).isLight();
   }
 
   @Override