diff --git a/calculate/templates/template_engine.py b/calculate/templates/template_engine.py
index cddd647..0a17d90 100644
--- a/calculate/templates/template_engine.py
+++ b/calculate/templates/template_engine.py
@@ -1571,7 +1571,7 @@ class TemplateEngine:
             self.environment = Environment(trim_blocks=True,
                                            lstrip_blocks=True)
 
-        self.environment.filters = CALCULATE_FILTERS
+        self.environment.filters.update(CALCULATE_FILTERS)
 
         self.calculate_extension = CalculateExtension(
                                                self.environment,