diff --git a/gradlib/gradlib/GemmTuner.py b/gradlib/gradlib/GemmTuner.py
index 0a5c630862..722c541b26 100644
--- a/gradlib/gradlib/GemmTuner.py
+++ b/gradlib/gradlib/GemmTuner.py
@@ -396,6 +396,13 @@ def asm_gemm_all_solutions(self):
                 )
                 if self.k / splitK < subK:
                     break
+                # splitK kernels use a semaphore array of size gdx*gdy; skip
+                # candidates where the grid exceeds the 1024-entry limit.
+                if splitK > 1:
+                    gdx = (self.n + tile_n - 1) // tile_n
+                    gdy = (self.m + tile_m - 1) // tile_m
+                    if gdx * gdy > 1024:
+                        continue
                 task_asm.append(
                     (
                         info,