diff --git a/devito/operator/xdsl_operator.py b/devito/operator/xdsl_operator.py
index da1519d978c..f572c1a4e99 100644
--- a/devito/operator/xdsl_operator.py
+++ b/devito/operator/xdsl_operator.py
@@ -117,7 +117,7 @@ def _jit_compile(self):
             xdsl_pipeline = XDSL_CPU_PIPELINE
             mlir_pipeline = MLIR_CPU_PIPELINE
 
-            block_sizes: list[int] = [min(target, self._jit_kernel_constants.get(dim, 1)) for target, dim in zip([32, 4, 8], ["x", "y", "z"])]
+            block_sizes: list[int] = [min(target, self._jit_kernel_constants.get(f"{dim}_size", 1)) for target, dim in zip([32, 4, 8], ["x", "y", "z"])]
             block_sizes = ','.join(str(bs) for bs in block_sizes)
 
             if is_omp: