diff --git a/libasn1fix/asn1fix_constraint.c b/libasn1fix/asn1fix_constraint.c
new file mode 100644
index 0000000..b7b66c4
--- /dev/null
+++ b/libasn1fix/asn1fix_constraint.c
@@ -0,0 +1,239 @@
+#include <asn1fix_internal.h>
+#include <asn1fix_constraint.h>
+#include <asn1fix_crange.h>
+
+static void _remove_exceptions(arg_t *arg, asn1p_constraint_t *ct);
+static int _constraint_value_resolve(arg_t *arg, asn1p_value_t **value);
+
+int
+asn1constraint_pullup(arg_t *arg) {
+	asn1p_expr_t *expr = arg->expr;
+	asn1p_constraint_t *ct_parent;
+	asn1p_constraint_t *ct_expr;
+	int ret;
+
+	if(expr->combined_constraints)
+		return 0;	/* Operation already performed earlier */
+
+	switch(expr->meta_type) {
+	case AMT_TYPE:
+	case AMT_TYPEREF:
+		break;
+	default:
+		return 0;	/* Nothing to do */
+	}
+
+	if(expr->expr_type == A1TC_REFERENCE) {
+		asn1p_ref_t *ref = expr->reference;
+		asn1p_module_t *mod_rw = arg->mod;
+		asn1p_expr_t *parent_expr;
+
+		assert(ref);
+		parent_expr = asn1f_lookup_symbol(arg, ref, &mod_rw);
+		if(!parent_expr) {
+			if(errno != EEXIST) {
+				DEBUG("\tWhile fetching parent constraints: "
+					"type \"%s\" not found: %s",
+					asn1f_printable_reference(ref),
+					strerror(errno));
+				return -1;
+			} else {
+				/*
+				 * -fknown-extern-type is given.
+				 * Assume there are no constraints there.
+				 */
+				WARNING("External type \"%s\": "
+					"assuming no constraints",
+					asn1f_printable_reference(ref));
+				ct_parent = 0;
+			}
+		} else {
+			arg->expr = parent_expr;
+			ret = asn1constraint_pullup(arg);
+			arg->expr = expr;
+			if(ret) return ret;
+
+			ct_parent = parent_expr->combined_constraints;
+		}
+	} else {
+		ct_parent = 0;
+	}
+
+	ct_expr = expr->constraints;
+
+	if(!ct_parent && !ct_expr)
+		return 0;	/* No constraints to consider */
+
+	if(ct_parent) {
+		ct_parent = asn1p_constraint_clone(ct_parent);
+		assert(ct_parent);
+	}
+
+	/*
+	 * If the current type does not have constraints, it inherits
+	 * the constraints of a parent.
+	 */
+	if(ct_parent && !ct_expr) {
+		expr->combined_constraints = ct_parent;
+		return 0;
+	}
+
+	ct_expr = asn1p_constraint_clone(ct_expr);
+	assert(ct_expr);
+
+	/*
+	 * Now we have a set of current expression's constraints,
+	 * and an optional set of the parent expression's constraints.
+	 */
+
+	if(ct_parent) {
+		/*
+		 * If we have a parent, remove all the extensions (46.4).
+		 */
+		_remove_exceptions(arg, ct_parent);
+
+		expr->combined_constraints = ct_parent;
+		if(ct_expr->type == ACT_CA_SET) {
+			int i;
+			for(i = 0; i < ct_expr->el_count; i++) {
+				if(asn1p_constraint_insert(
+					expr->combined_constraints,
+						ct_expr->elements[i])) {
+					expr->combined_constraints = 0;
+					asn1p_constraint_free(ct_expr);
+					asn1p_constraint_free(ct_parent);
+					return -1;
+				} else {
+					ct_expr->elements[i] = 0;
+				}
+			}
+			asn1p_constraint_free(ct_expr);
+		} else {
+			asn1p_constraint_insert(expr->combined_constraints,
+				ct_expr);
+		}
+	} else {
+		expr->combined_constraints = ct_expr;
+	}
+
+	return 0;
+}
+
+int
+asn1constraint_resolve(arg_t *arg, asn1p_constraint_t *ct) {
+	asn1p_expr_t *top_parent;
+	int rvalue = 0;
+	int ret;
+	int el;
+
+	if(!ct) return 0;
+
+	/* Don't touch information object classes */
+	switch(ct->type) {
+	case ACT_CT_WCOMP:
+	case ACT_CT_WCOMPS:
+	case ACT_CA_CRC:
+		return 0;
+	default:
+		break;
+	}
+
+	top_parent = asn1f_find_terminal_type(arg, arg->expr, 0);
+	if(top_parent) {
+		ret = asn1constraint_compatible(top_parent->expr_type,
+			ct->type);
+		switch(ret) {
+		case -1:	/* If unknown, assume OK. */
+		case  1:
+			break;
+		case 0:
+		default:
+			FATAL("%s at line %d: "
+				"Constraint type %s is not applicable to %s",
+				arg->expr->Identifier, ct->_lineno,
+				asn1p_constraint_type2str(ct->type),
+				ASN_EXPR_TYPE2STR(top_parent->expr_type)
+			);
+			rvalue = -1;
+			break;
+		}
+	} else {
+		WARNING("%s at line %d: "
+			"Constraints ignored: Unresolved parent type",
+			arg->expr->Identifier, arg->expr->_lineno);
+	}
+
+	if(ct->value && ct->value->type == ATV_REFERENCED) {
+		ret = _constraint_value_resolve(arg, &ct->value);
+		RET2RVAL(ret, rvalue);
+	}
+	if(ct->range_start && ct->range_start->type == ATV_REFERENCED) {
+		ret = _constraint_value_resolve(arg, &ct->range_start);
+		RET2RVAL(ret, rvalue);
+	}
+	if(ct->range_stop && ct->range_stop->type == ATV_REFERENCED) {
+		ret = _constraint_value_resolve(arg, &ct->range_stop);
+		RET2RVAL(ret, rvalue);
+	}
+
+	for(el = 0; el < ct->el_count; el++) {
+		ret = asn1constraint_resolve(arg, ct->elements[el]);
+		RET2RVAL(ret, rvalue);
+	}
+
+	return rvalue;
+}
+
+static void
+_remove_exceptions(arg_t *arg, asn1p_constraint_t *ct) {
+	int i;
+
+	for(i = 0; i < ct->el_count; i++) {
+		if(ct->elements[i]->type == ACT_EL_EXT)
+			break;
+		_remove_exceptions(arg, ct->elements[i]);
+	}
+
+	/* Remove the elements at and after the extensibility mark */
+	for(; i < ct->el_count; ct->el_count--) {
+		asn1p_constraint_t *rm;
+		rm = ct->elements[ct->el_count-1];
+		asn1p_constraint_free(rm);
+	}
+
+	if(i < ct->el_size)
+		ct->elements[i] = 0;
+}
+
+
+static int
+_constraint_value_resolve(arg_t *arg, asn1p_value_t **value) {
+	asn1p_expr_t static_expr;
+	asn1p_expr_t *tmp_expr;
+	asn1p_module_t *mod_rw = arg->mod;
+	arg_t tmp_arg;
+	int rvalue = 0;
+	int ret;
+
+	tmp_expr = asn1f_lookup_symbol(arg, (*value)->value.reference, &mod_rw);
+	if(tmp_expr == NULL) {
+		FATAL("Cannot find symbol %s "
+			"used in %s subtype constraint at line %d",
+			asn1f_printable_reference((*value)->value.reference),
+			arg->expr->Identifier, arg->expr->_lineno);
+		assert((*value)->type == ATV_REFERENCED);
+		return -1;
+	}
+
+	static_expr = *tmp_expr;
+	static_expr.value = *value;
+	tmp_arg = *arg;
+	tmp_arg.mod = mod_rw;
+	tmp_arg.expr = &static_expr;
+	ret = asn1f_fix_dereference_values(&tmp_arg);
+	RET2RVAL(ret, rvalue);
+	assert(static_expr.value);
+	*value = static_expr.value;
+
+	return rvalue;
+}