diff --git a/python/sglang/srt/speculative/eagle_info_v2.py b/python/sglang/srt/speculative/eagle_info_v2.py
index bc9f35e67996..331ba0e789ef 100644
--- a/python/sglang/srt/speculative/eagle_info_v2.py
+++ b/python/sglang/srt/speculative/eagle_info_v2.py
@@ -279,6 +279,11 @@ def prepare_for_v2_verify(
                 batch.mamba_track_mask = None
                 batch.mamba_track_seqlens = None
 
+            # Populate seq_lens_cpu/seq_lens_sum on the verify input so that
+            # TBO's split_spec_info can slice the custom_mask correctly.
+            self.seq_lens_cpu = batch.seq_lens_cpu
+            self.seq_lens_sum = batch.seq_lens_sum
+
         # Get a forward batch
         batch.forward_mode = (
             ForwardMode.IDLE