diff --git a/hw/rtl/core/VX_scoreboard.sv b/hw/rtl/core/VX_scoreboard.sv
index 379444ba..7888788f 100644
--- a/hw/rtl/core/VX_scoreboard.sv
+++ b/hw/rtl/core/VX_scoreboard.sv
@@ -248,6 +248,20 @@ module VX_scoreboard import VX_gpu_pkg::*; #(
             .ready_out (scoreboard_if[i].ready)
         );
 
+        // inflight_tensor overflow/underflow check
+        `RUNTIME_ASSERT(
+            !(writeback_fire && writeback_if[i].data.tensor) ||
+            inflight_tensor[writeback_if[i].data.wis] != INFLT_WIDTH'(0),
+            ("%t: *** core%0d: wid=%0d, underflow at inflight_tensor!",
+             $time, CORE_ID, wis_to_wid(writeback_if[i].data.wis, i))
+        )
+        `RUNTIME_ASSERT(
+            !(ibuffer_if[i].valid && ibuffer_if[i].ready && hgmma_start) ||
+            inflight_tensor[ibuffer_if[i].data.wis] != INFLT_MAX,
+            ("%t: *** core%0d: wid=%0d, overflow at inflight_tensor!",
+             $time, CORE_ID, wis_to_wid(ibuffer_if[i].data.wis, i))
+        )
+
         always @(posedge clk) begin
             if (reset) begin
                 inuse_regs <= '0;
@@ -261,8 +275,8 @@ module VX_scoreboard import VX_gpu_pkg::*; #(
                 end
             `ifdef EXT_T_HOPPER
                 if (writeback_fire && writeback_if[i].data.tensor) begin
-                    inflight_tensor[ibuffer_if[i].data.wis] <=
-                        inflight_tensor[ibuffer_if[i].data.wis] - INFLT_WIDTH'(1);
+                    inflight_tensor[writeback_if[i].data.wis] <=
+                        inflight_tensor[writeback_if[i].data.wis] - INFLT_WIDTH'(1);
                 end
                 if (ibuffer_if[i].valid && ibuffer_if[i].ready && hgmma_start) begin
                     inflight_tensor[ibuffer_if[i].data.wis] <=