diff --git a/src/ifcopenshell-python/ifcopenshell/entity_instance.py b/src/ifcopenshell-python/ifcopenshell/entity_instance.py
index ea58268322..2b5015cb85 100644
--- a/src/ifcopenshell-python/ifcopenshell/entity_instance.py
+++ b/src/ifcopenshell-python/ifcopenshell/entity_instance.py
@@ -152,6 +152,8 @@ class entity_instance(object):
                             idx, entity_instance.unwrap_value(value)
                         )
                 except BaseException as e:
+                    import traceback
+                    traceback.print_exc()
                     valid = False
 
             if not valid:
diff --git a/src/ifcparse/IfcParse.cpp b/src/ifcparse/IfcParse.cpp
index 1ce886a0fb..b8074cb1b6 100644
--- a/src/ifcparse/IfcParse.cpp
+++ b/src/ifcparse/IfcParse.cpp
@@ -1212,6 +1212,11 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
 	case IfcUtil::Argument_BOOL:
 		copy->set(static_cast<bool>(*a));
 		break;
+	case IfcUtil::Argument_LOGICAL: {
+		boost::logic::tribool tb = *a;
+		copy->set(tb);
+		break;
+	}
 	case IfcUtil::Argument_DOUBLE:
 		copy->set(static_cast<double>(*a));
 		break;
diff --git a/src/ifcparse/IfcWrite.cpp b/src/ifcparse/IfcWrite.cpp
index 6fa3ac7dd3..4ff08eec48 100644
--- a/src/ifcparse/IfcWrite.cpp
+++ b/src/ifcparse/IfcWrite.cpp
@@ -229,6 +229,7 @@ void StringBuilderVisitor::operator()(const std::vector< std::vector<double> >&
 
 IfcWriteArgument::operator int() const { return as<int>(); }
 IfcWriteArgument::operator bool() const { return as<bool>(); }
+IfcWriteArgument::operator boost::logic::tribool() const { return as<boost::logic::tribool>(); }
 IfcWriteArgument::operator double() const { return as<double>(); }
 IfcWriteArgument::operator std::string() const { 
 	if (type() == IfcUtil::Argument_ENUMERATION) {
diff --git a/src/ifcparse/IfcWrite.h b/src/ifcparse/IfcWrite.h
index c9300df91e..502ec21f1e 100644
--- a/src/ifcparse/IfcWrite.h
+++ b/src/ifcparse/IfcWrite.h
@@ -145,6 +145,8 @@ namespace IfcWrite {
 		
 		operator int() const;
 		operator bool() const;
+		operator boost::logic::tribool() const;
+
 		operator double() const;
 		operator std::string() const;
 		operator boost::dynamic_bitset<>() const;
diff --git a/src/ifcwrap/IfcParseWrapper.i b/src/ifcwrap/IfcParseWrapper.i
index 8c88abb0ec..49e3cf20c5 100644
--- a/src/ifcwrap/IfcParseWrapper.i
+++ b/src/ifcwrap/IfcParseWrapper.i
@@ -326,6 +326,17 @@ static IfcUtil::ArgumentType helper_fn_attribute_type(const IfcUtil::IfcBaseClas
 		}
 	}
 
+	void setArgumentAsLogical(unsigned int i, boost::logic::tribool v) {
+		IfcUtil::ArgumentType arg_type = helper_fn_attribute_type($self, i);
+		if (arg_type == IfcUtil::Argument_LOGICAL) {
+			IfcWrite::IfcWriteArgument* arg = new IfcWrite::IfcWriteArgument();
+			arg->set(v);
+			self->data().setArgument(i, arg);	
+		} else {
+			throw IfcParse::IfcException("Attribute not set");
+		}
+	}
+
 	void setArgumentAsDouble(unsigned int i, double v) {
 		IfcUtil::ArgumentType arg_type = helper_fn_attribute_type($self, i);
 		if (arg_type == IfcUtil::Argument_DOUBLE) {
diff --git a/src/ifcwrap/utils/type_conversion.i b/src/ifcwrap/utils/type_conversion.i
index 91355cdf8c..14a4f5c86c 100644
--- a/src/ifcwrap/utils/type_conversion.i
+++ b/src/ifcwrap/utils/type_conversion.i
@@ -123,6 +123,7 @@
 	PyObject* pythonize(const int& t)                   { return PyInt_FromLong(t);                                                                  }
 	PyObject* pythonize(const unsigned int& t)          { return PyInt_FromLong(t);                                                                  }
 	PyObject* pythonize(const bool& t)                  { return PyBool_FromLong(t);                                                                 }
+	PyObject* pythonize(const boost::logic::tribool& t) { return boost::logic::indeterminate(t) ? PyUnicode_FromString("UNKNOWN") : PyBool_FromLong((bool)t) ;}
 	PyObject* pythonize(const double& t)                { return PyFloat_FromDouble(t);                                                              }
 	PyObject* pythonize(const std::string& t)           { return PyUnicode_FromString(t.c_str());                                                    }
 	PyObject* pythonize(const IfcUtil::IfcBaseClass* t) { return SWIG_NewPointerObj(SWIG_as_voidptr(t), SWIGTYPE_p_IfcUtil__IfcBaseClass, 0);        }
diff --git a/src/ifcwrap/utils/typemaps_in.i b/src/ifcwrap/utils/typemaps_in.i
index 03289a17f5..19588c1584 100644
--- a/src/ifcwrap/utils/typemaps_in.i
+++ b/src/ifcwrap/utils/typemaps_in.i
@@ -241,6 +241,28 @@ CREATE_VECTOR_TYPEMAP_IN(std::string, STRING, str)
    $1 = check_aggregate_of_aggregate_of_type($input, get_python_type<double>());
 }
 
+%typemap(in) boost::logic::tribool {
+	if (PyBool_Check($input)) {
+		$1 = $input == Py_True;
+	} else if (PyUnicode_Check($input)) {
+		// we already checked the value of the string in the typecheck typemap
+		$1 = boost::logic::indeterminate;
+	} else {
+		SWIG_exception(SWIG_TypeError, "Logical needs boolean or \"UNKOWN\"");
+	}
+}
+
+%typemap(typecheck, precedence=SWIG_TYPECHECK_INTEGER) boost::logic::tribool {
+    $1 = PyBool_Check($input);
+	if (!$1 && PyUnicode_Check($input)) {
+		PyObject * ascii = PyUnicode_AsEncodedString(result, "UTF-8", "strict");
+		if (ascii) {
+			$1 = strcmp(PyBytes_AS_STRING(ascii), "UNKNOWN") == 0;
+			Py_DECREF(ascii);
+		}	
+	}
+}
+
 %define CREATE_OPTIONAL_TYPEMAP_IN(template_type, express_name, python_name)
 
 	%typemap(in) const boost::optional<template_type>& {
diff --git a/src/ifcwrap/utils/typemaps_out.i b/src/ifcwrap/utils/typemaps_out.i
index 8243cba33f..07f07a1bcc 100644
--- a/src/ifcwrap/utils/typemaps_out.i
+++ b/src/ifcwrap/utils/typemaps_out.i
@@ -51,6 +51,10 @@
 			bool v = arg;
 			$result = pythonize(v);
 		break; }
+		case IfcUtil::Argument_LOGICAL: {
+			boost::logic::tribool v = arg;
+			$result = pythonize(v);
+		break; }
 		case IfcUtil::Argument_DOUBLE: {
 			double v = arg;
 			$result = pythonize(v);