diff --git a/backends/json/json.cc b/backends/json/json.cc
index 1781a28cd..dda4dfedd 100644
--- a/backends/json/json.cc
+++ b/backends/json/json.cc
@@ -126,6 +126,10 @@ struct JsonWriter
 			f << stringf("%s\n", first ? "" : ",");
 			f << stringf("        %s: {\n", get_name(n).c_str());
 			f << stringf("          \"direction\": \"%s\",\n", w->port_input ? w->port_output ? "inout" : "input" : "output");
+			if (w->start_offset)
+				f << stringf("          \"offset\": %d,\n", w->start_offset);
+			if (w->upto)
+				f << stringf("          \"upto\": 1,\n");
 			f << stringf("          \"bits\": %s\n", get_bits(w).c_str());
 			f << stringf("        }");
 			first = false;
diff --git a/frontends/json/jsonparse.cc b/frontends/json/jsonparse.cc
index b74d41dd2..f5ae8eb72 100644
--- a/frontends/json/jsonparse.cc
+++ b/frontends/json/jsonparse.cc
@@ -292,6 +292,18 @@ void json_import(Design *design, string &modname, JsonNode *node)
 			if (port_wire == nullptr)
 				port_wire = module->addWire(port_name, GetSize(port_bits_node->data_array));
 
+			if (port_node->data_dict.count("upto") != 0) {
+				JsonNode *val = port_node->data_dict.at("upto");
+				if (val->type == 'N')
+					port_wire->upto = val->data_number != 0;
+			}
+
+			if (port_node->data_dict.count("offset") != 0) {
+				JsonNode *val = port_node->data_dict.at("offset");
+				if (val->type == 'N')
+					port_wire->start_offset = val->data_number;
+			}
+
 			if (port_direction_node->data_string == "input") {
 				port_wire->port_input = true;
 			} else