diff --git a/src/lib/definition.cpp b/src/lib/definition.cpp
--- a/src/lib/definition.cpp
+++ b/src/lib/definition.cpp
@@ -171,7 +171,12 @@
 
 bool Definition::isDelimiter(QChar c) const
 {
-    d->load();
+    // We want isDelimiter() to work for invalid definitions as well. Therefore,
+    // call load() only for a valid Definition to read the delimiters from the xml files.
+    // For an invalid Definition, fallback to the default delimiters.
+    if (isValid()) {
+        d->load();
+    }
     return d->isDelimiter(c);
 }