diff --git a/pricing/pricing.py b/pricing/pricing.py
index 7757aec..9fd431f 100644
--- a/pricing/pricing.py
+++ b/pricing/pricing.py
@@ -152,8 +152,12 @@ def check_value(field, spec_value, data_value):
 	mode = field.value_mode
 	if not mode or mode == '=':
 		mode = '=='
-	script = f'{data_value} {mode} {typevalue(spec_value, field.type)}'
-	x = eval(script)
+	ns = {
+		"a": data_value
+		"b": typevalue(spec_value, field.type)
+	}
+	script = f'a {mode} b'
+	x = eval(script, ns)
 	return x
 	
 class PricingProgram: