diff --git a/src/ifcopenshell-python/ifcopenshell/util/selector.py b/src/ifcopenshell-python/ifcopenshell/util/selector.py
index 419937aac3..8a32c4674d 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/selector.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/selector.py
@@ -55,7 +55,7 @@ class Selector:
                     equal: "="
                     morethan: ">"
                     lessthan: "<"
-                    BOOLEAN: "TRUE" | "FALSE"
+                    BOOLEAN: "TRUE" | "FALSE" | "true" | "false"| "True" | "False"
                     NULL: "NULL"
 
                     // Embed common.lark for packaging