diff --git a/pform_types.h b/pform_types.h
index 0bd87d817..92061527e 100644
--- a/pform_types.h
+++ b/pform_types.h
@@ -380,4 +380,8 @@ extern std::ostream& operator<< (std::ostream&out, const pform_name_t&);
 extern std::ostream& operator<< (std::ostream&out, const name_component_t&that);
 extern std::ostream& operator<< (std::ostream&out, const index_component_t&that);
 
+#if __cplusplus < 201103L
+#undef unique_ptr
+#endif
+
 #endif /* IVL_pform_types_H */
diff --git a/vhdlpp/expression.h b/vhdlpp/expression.h
index 35f23e22c..3ae6c2bb9 100644
--- a/vhdlpp/expression.h
+++ b/vhdlpp/expression.h
@@ -1097,4 +1097,8 @@ private:
     Expression*delay_;
 };
 
+#if __cplusplus < 201103L
+#undef unique_ptr
+#endif
+
 #endif /* IVL_expression_H */