diff --git a/openfpga/src/base/openfpga_naming.cpp b/openfpga/src/base/openfpga_naming.cpp
index 9bfad01a2..530db8cc6 100644
--- a/openfpga/src/base/openfpga_naming.cpp
+++ b/openfpga/src/base/openfpga_naming.cpp
@@ -496,7 +496,7 @@ std::string generate_grid_duplicated_port_name(const size_t& width,
   port_name += std::to_string(width);
   port_name += std::string("_height_");
   port_name += std::to_string(height);
-  port_name += std::string("_pin_");
+  port_name += std::string("__pin_");
   port_name += std::to_string(pin_id);
   port_name += std::string("_");