diff --git a/src/pystencils/codegen/gpu_indexing.py b/src/pystencils/codegen/gpu_indexing.py
index 52efee81d450403da3f48fc1dc88bc3155445f15..bcffbbcaebb5a0222cb6f864755e4694fa9c674d 100644
--- a/src/pystencils/codegen/gpu_indexing.py
+++ b/src/pystencils/codegen/gpu_indexing.py
@@ -140,7 +140,7 @@ class AutomaticLaunchConfiguration(GpuLaunchConfiguration):
 
     @block_size.setter
     def block_size(self, val: dim3):
-        warn("Setting `block_size` on an automatic launch configuration has no effect.", UserWarning)
+        AttributeError("Setting `block_size` on an automatic launch configuration has no effect.")
 
     @property
     def parameters(self) -> frozenset[Parameter]:
@@ -298,7 +298,7 @@ class DynamicBlockSizeLaunchConfiguration(GpuLaunchConfiguration):
 
     @block_size.setter
     def block_size(self, val: dim3):
-        warn("Setting `block_size` on an dynamic launch configuration has no effect.", UserWarning)
+        AttributeError("Setting `block_size` on an dynamic launch configuration has no effect.")
 
     @staticmethod
     def _round_block_sizes_to_warp_size(