diff --git a/gemma/gemma.h b/gemma/gemma.h
index d1a33a6..d7be609 100644
--- a/gemma/gemma.h
+++ b/gemma/gemma.h
@@ -100,7 +100,7 @@ struct RuntimeConfig {
 
   // These defaults are overridden by InferenceArgs::CopyTo(*this):
   // Max tokens per batch during prefill.
-  size_t prefill_tbatch_size = 32;
+  size_t prefill_tbatch_size = 256;
   // Max queries per batch (one token from each) during decode.
   size_t decode_qbatch_size = 16;
 
diff --git a/util/app.h b/util/app.h
index 49a75b5..5c0698f 100644
--- a/util/app.h
+++ b/util/app.h
@@ -273,7 +273,7 @@ struct InferenceArgs : public ArgsBase<InferenceArgs> {
     visitor(max_generated_tokens, "max_generated_tokens", size_t{2048},
             "Maximum number of tokens to generate.");
 
-    visitor(prefill_tbatch_size, "prefill_tbatch", size_t{64},
+    visitor(prefill_tbatch_size, "prefill_tbatch", size_t{256},
             "Prefill: max tokens per batch.");
     visitor(decode_qbatch_size, "decode_qbatch", size_t{16},
             "Decode: max queries per batch.");