diff --git a/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.cpp b/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.cpp
index 4330ca5cc..d687a1468 100644
--- a/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.cpp
+++ b/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.cpp
@@ -2432,7 +2432,7 @@ const RRGSB DeviceRRGSB::get_sb_unique_module(size_t index) const {
 }
 
 /* Get a rr switch block which a unique mirror */ 
-const RRGSB DeviceRRGSB::get_cb_unique_module(t_rr_type cb_type, size_t index) const {
+const RRGSB& DeviceRRGSB::get_cb_unique_module(t_rr_type cb_type, size_t index) const {
   assert (validate_cb_unique_module_index(cb_type, index));
   assert (validate_cb_type(cb_type));
   switch(cb_type) {
@@ -2449,7 +2449,7 @@ const RRGSB DeviceRRGSB::get_cb_unique_module(t_rr_type cb_type, size_t index) c
 }
 
 /* Give a coordinator of a rr switch block, and return its unique mirror */ 
-const RRGSB DeviceRRGSB::get_cb_unique_module(t_rr_type cb_type, DeviceCoordinator& coordinator) const {
+const RRGSB& DeviceRRGSB::get_cb_unique_module(t_rr_type cb_type, DeviceCoordinator& coordinator) const {
   assert (validate_cb_type(cb_type));
   assert(validate_coordinator(coordinator));
   size_t cb_unique_module_id;
@@ -2659,7 +2659,8 @@ void DeviceRRGSB::build_cb_unique_module(t_rr_type cb_type) {
 
       /* Traverse the unique_mirror list and check it is an mirror of another */
       for (size_t id = 0; id < get_num_cb_unique_module(cb_type); ++id) {
-        if (true == rr_gsb_[ix][iy].is_cb_mirror(get_cb_unique_module(cb_type, id), cb_type)) {
+        const RRGSB& unique_module = get_cb_unique_module(cb_type, id);
+        if (true == rr_gsb_[ix][iy].is_cb_mirror(unique_module, cb_type)) {
           /* This is a mirror, raise the flag and we finish */
           is_unique_module = false;
           /* Record the id of unique mirror */
@@ -3109,7 +3110,7 @@ bool DeviceRRGSB::validate_cb_unique_module_index(t_rr_type cb_type, size_t inde
     }
     return true;
   case CHANY:
-    if (index >= cbx_unique_module_.size()) {
+    if (index >= cby_unique_module_.size()) {
       return false;
     }
     return true;
diff --git a/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.h b/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.h
index c6cb9978c..49c1d78f4 100644
--- a/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.h
+++ b/vpr7_x2p/vpr/SRC/fpga_x2p/base/rr_blocks.h
@@ -339,8 +339,8 @@ class DeviceRRGSB {
     const RRGSB get_sb_unique_submodule(DeviceCoordinator& coordinator, enum e_side side, size_t seg_id) const; /* Get a rr switch block which a unique mirror */ 
     const RRGSB get_sb_unique_module(size_t index) const; /* Get a rr switch block which a unique mirror */ 
     const RRGSB get_sb_unique_module(DeviceCoordinator& coordinator) const; /* Get a rr switch block which a unique mirror */ 
-    const RRGSB get_cb_unique_module(t_rr_type cb_type, size_t index) const; /* Get a rr switch block which a unique mirror */ 
-    const RRGSB get_cb_unique_module(t_rr_type cb_type, DeviceCoordinator& coordinator) const;
+    const RRGSB& get_cb_unique_module(t_rr_type cb_type, size_t index) const; /* Get a rr switch block which a unique mirror */ 
+    const RRGSB& get_cb_unique_module(t_rr_type cb_type, DeviceCoordinator& coordinator) const;
     size_t get_max_num_sides() const; /* Get the maximum number of sides across the switch blocks */
     size_t get_num_segments() const; /* Get the size of segment_ids */
     size_t get_segment_id(size_t index) const; /* Get a segment id */
diff --git a/vpr7_x2p/vpr/SRC/fpga_x2p/verilog/verilog_routing.c b/vpr7_x2p/vpr/SRC/fpga_x2p/verilog/verilog_routing.c
index 9d3431585..81324565f 100644
--- a/vpr7_x2p/vpr/SRC/fpga_x2p/verilog/verilog_routing.c
+++ b/vpr7_x2p/vpr/SRC/fpga_x2p/verilog/verilog_routing.c
@@ -1453,6 +1453,10 @@ void dump_verilog_unique_switch_box_interc(t_sram_orgz_info* cur_sram_orgz_info,
   } else {
     num_drive_rr_nodes = cur_rr_node->num_drive_rr_nodes;
     drive_rr_nodes = cur_rr_node->drive_rr_nodes;
+    /* Special: if there are zero-driver nodes. We skip here */
+    if (0 == num_drive_rr_nodes) {
+      return; 
+    }
   }
 
   if (0 == num_drive_rr_nodes) {