diff --git a/cutedsl/bridge.py b/cutedsl/bridge.py
index 2822d8c5..b96211b7 100644
--- a/cutedsl/bridge.py
+++ b/cutedsl/bridge.py
@@ -369,11 +369,14 @@ def run_nvfp4_grouped_gemm(
     no cute.compile() in the forward path.
     """
     num_experts = mat_b.shape[0]
-    n_dim = mat_b.shape[2]  # packed N (in float4 elements)
+    n_dim = mat_b.shape[2]  # packed N (in float4_e2m1fn_x2 elements)
+    # float4_e2m1fn_x2 packs 2 FP4 values per storage element
+    # The GEMM accumulates in BF16, so output has 2x the packed dimension
+    n_dim_logical = n_dim * 2
     tokens_sum = mat_a.shape[0]
     device = mat_a.device
 
-    out = torch.zeros(tokens_sum, n_dim, dtype=torch.bfloat16, device=device)
+    out = torch.zeros(tokens_sum, n_dim_logical, dtype=torch.bfloat16, device=device)
 
     compiled, kernel, max_active_clusters = _get_compiled_kernel(
         num_experts, device, mma_tiler_mn, cluster_shape_mn