diff --git a/source/net/filebot/ui/rename/RenameAction.java b/source/net/filebot/ui/rename/RenameAction.java
index 1ae402ec..16fa4ad6 100644
--- a/source/net/filebot/ui/rename/RenameAction.java
+++ b/source/net/filebot/ui/rename/RenameAction.java
@@ -72,9 +72,15 @@ class RenameAction extends AbstractAction {
 
 		Window window = getWindow(evt.getSource());
 		withWaitCursor(window, () -> {
-			Map<File, File> renameMap = validate(model.getRenameMap(), window);
+			// prepare rename map (abort and notify the user if background computation is still in progress)
+			Map<File, File> renameMap = null;
+			try {
+				renameMap = validate(model.getRenameMap(), window);
+			} catch (Exception e) {
+				log.log(Level.WARNING, e::getMessage);
+			}
 
-			if (renameMap.isEmpty()) {
+			if (renameMap == null || renameMap.isEmpty()) {
 				return;
 			}
 
diff --git a/source/net/filebot/ui/rename/RenameModel.java b/source/net/filebot/ui/rename/RenameModel.java
index 8d38bade..a7f4bf6b 100644
--- a/source/net/filebot/ui/rename/RenameModel.java
+++ b/source/net/filebot/ui/rename/RenameModel.java
@@ -92,7 +92,7 @@ public class RenameModel extends MatchModel<Object, File> {
 				} catch (ExecutionException e) {
 					throw new IllegalStateException(String.format("\"%s\" could not be formatted: %s.", task.preview(), e.getCause().getMessage()));
 				} catch (TimeoutException e) {
-					throw new IllegalStateException(String.format("\"%s\" has not been formatted yet.", task.preview()));
+					throw new IllegalStateException(String.format("\"%s\" has not been formatted yet. Applying custom formats may take a while.", task.preview()));
 				} catch (InterruptedException e) {
 					throw new RuntimeException(e);
 				}