diff --git a/libasn1fix/asn1fix_compat.h b/libasn1fix/asn1fix_compat.h
new file mode 100644
index 0000000..429e7dd
--- /dev/null
+++ b/libasn1fix/asn1fix_compat.h
@@ -0,0 +1,14 @@
+#ifndef	_ASN1FIX_COMPAT_H_
+#define	_ASN1FIX_COMPAT_H_
+
+/*
+ * Check that the expressions given are compatible in their type.
+ * ORDER DOES MATTER!
+ * The compatibility is being checked as if the value of b were used
+ * to assign it to type a.
+ */
+int asn1f_check_type_compatibility(arg_t *arg,
+	asn1p_expr_t *a,
+	asn1p_expr_t *b);
+
+#endif	/* _ASN1FIX_COMPAT_H_ */