diff --git a/src/ifcwrap/IfcParseWrapper.i b/src/ifcwrap/IfcParseWrapper.i
index 7bc397a143..8699151993 100644
--- a/src/ifcwrap/IfcParseWrapper.i
+++ b/src/ifcwrap/IfcParseWrapper.i
@@ -357,7 +357,7 @@ static IfcUtil::ArgumentType helper_fn_attribute_type(const IfcUtil::IfcBaseClas
         return oss.str();
 	}
 
-	std::string to_string(bool valid_spf) const {
+	std::string to_string(bool valid_spf = true) const {
 		std::ostringstream oss;
 		$self->toString(oss, valid_spf);
         return oss.str();