diff --git a/xc7/archdefs.h b/xc7/archdefs.h
index 571d76d3..1c2a752d 100644
--- a/xc7/archdefs.h
+++ b/xc7/archdefs.h
@@ -70,6 +70,7 @@ struct BelId
 
     bool operator==(const BelId &other) const { return index == other.index; }
     bool operator!=(const BelId &other) const { return index != other.index; }
+    bool operator<(const BelId &other) const { return index < other.index; }
 };
 
 struct WireId
@@ -78,6 +79,7 @@ struct WireId
 
     bool operator==(const WireId &other) const { return index == other.index; }
     bool operator!=(const WireId &other) const { return index != other.index; }
+    bool operator<(const WireId &other) const { return index < other.index; }
 };
 
 struct PipId
@@ -86,6 +88,7 @@ struct PipId
 
     bool operator==(const PipId &other) const { return index == other.index; }
     bool operator!=(const PipId &other) const { return index != other.index; }
+    bool operator<(const PipId &other) const { return index < other.index; }
 };
 
 struct GroupId