diff --git a/vllm/v1/worker/gpu/attn_utils.py b/vllm/v1/worker/gpu/attn_utils.py
index c2ba12437f..6fc55ee320 100644
--- a/vllm/v1/worker/gpu/attn_utils.py
+++ b/vllm/v1/worker/gpu/attn_utils.py
@@ -199,7 +199,12 @@ def _reshape_kv_cache(
 
             if isinstance(kv_cache_spec, AttentionSpec):
                 has_attn = True
-                num_blocks_per_kv_block = kv_cache_spec.block_size // kernel_block_size
+                # Use storage_block_size: it equals block_size for uncompressed
+                # specs but is smaller for compressed ones (DeepSeek V4), which
+                # store block_size tokens in block_size // compress_ratio slots.
+                num_blocks_per_kv_block = (
+                    kv_cache_spec.storage_block_size // kernel_block_size
+                )
                 kernel_num_blocks = num_blocks * num_blocks_per_kv_block
                 kv_cache_shape = group.backend.get_kv_cache_shape(
                     kernel_num_blocks,