diff --git a/sherpa-onnx/csrc/hypothesis.h b/sherpa-onnx/csrc/hypothesis.h
index 1487bfcc4..ada88c8ce 100644
--- a/sherpa-onnx/csrc/hypothesis.h
+++ b/sherpa-onnx/csrc/hypothesis.h
@@ -36,10 +36,12 @@ struct Hypothesis {
 
   // lm_probs[i] contains the lm score for each token in ys.
   // Used only in transducer mofified beam-search.
+  // Elements filled only if LM is used.
   std::vector<float> lm_probs;
 
   // context_scores[i] contains the context-graph score for each token in ys.
   // Used only in transducer mofified beam-search.
+  // Elements filled only if `ContextGraph` is used.
   std::vector<float> context_scores;
 
   // The total score of ys in log space.
diff --git a/sherpa-onnx/csrc/online-recognizer.cc b/sherpa-onnx/csrc/online-recognizer.cc
index 52749d171..7c0dd78d4 100644
--- a/sherpa-onnx/csrc/online-recognizer.cc
+++ b/sherpa-onnx/csrc/online-recognizer.cc
@@ -20,7 +20,7 @@ namespace sherpa_onnx {
 
 /// Helper for `OnlineRecognizerResult::AsJsonString()`
 template<typename T>
-const std::string& VecToString(const std::vector<T>& vec, int32_t precision = 6) {
+std::string VecToString(const std::vector<T>& vec, int32_t precision = 6) {
   std::ostringstream oss;
   oss << std::fixed << std::setprecision(precision);
   oss << "[ ";
@@ -35,9 +35,8 @@ const std::string& VecToString(const std::vector<T>& vec, int32_t precision = 6)
 
 /// Helper for `OnlineRecognizerResult::AsJsonString()`
 template<>  // explicit specialization for T = std::string
-const std::string& VecToString<std::string>(const std::vector<std::string>& vec,
-                                            int32_t) // ignore 2nd arg
-{
+std::string VecToString<std::string>(const std::vector<std::string>& vec,
+                                     int32_t) {  // ignore 2nd arg
   std::ostringstream oss;
   oss << "[ ";
   std::string sep = "";
@@ -57,9 +56,10 @@ std::string OnlineRecognizerResult::AsJsonString() const {
   os << "\"timestamps\": " << VecToString(timestamps, 2) << ", ";
   os << "\"ys_probs\": " << VecToString(ys_probs, 6) << ", ";
   os << "\"lm_probs\": " << VecToString(lm_probs, 6) << ", ";
-  os << "\"constext_scores\": " << VecToString(context_scores, 6) << ", ";
+  os << "\"context_scores\": " << VecToString(context_scores, 6) << ", ";
   os << "\"segment\": " << segment << ", ";
-  os << "\"start_time\": " << std::fixed << std::setprecision(2) << start_time  << ", ";
+  os << "\"start_time\": " << std::fixed << std::setprecision(2)
+     << start_time  << ", ";
   os << "\"is_final\": " << (is_final ? "true" : "false");
   os << "}";
   return os.str();
diff --git a/sherpa-onnx/csrc/online-transducer-modified-beam-search-decoder.cc b/sherpa-onnx/csrc/online-transducer-modified-beam-search-decoder.cc
index b4aa49114..e37ba63d4 100644
--- a/sherpa-onnx/csrc/online-transducer-modified-beam-search-decoder.cc
+++ b/sherpa-onnx/csrc/online-transducer-modified-beam-search-decoder.cc
@@ -190,17 +190,22 @@ void OnlineTransducerModifiedBeamSearchDecoder::Decode(
         if (new_token != 0 && new_token != unk_id_) {
           const Hypothesis& prev_i = prev[hyp_index];
           // subtract 'prev[i]' path scores, which were added before
-          // for getting topk tokens
+          // getting topk tokens
           float y_prob = p_logprob[k] - prev_i.log_prob - prev_i.lm_log_prob;
           new_hyp.ys_probs.push_back(y_prob);
 
-          float lm_prob = new_hyp.lm_log_prob - prev_lm_log_prob;
-          if (lm_scale_ != 0.0) {
-            lm_prob /= lm_scale_;  // remove lm-scale
+          if (lm_) {  // export only when LM is used
+            float lm_prob = new_hyp.lm_log_prob - prev_lm_log_prob;
+            if (lm_scale_ != 0.0) {
+              lm_prob /= lm_scale_;  // remove lm-scale
+            }
+            new_hyp.lm_probs.push_back(lm_prob);
           }
-          new_hyp.lm_probs.push_back(lm_prob);
 
-          new_hyp.context_scores.push_back(context_score);
+          // export only when `ContextGraph` is used
+          if (ss != nullptr && ss[b]->GetContextGraph() != nullptr) {
+            new_hyp.context_scores.push_back(context_score);
+          }
         }
 
         hyps.Add(std::move(new_hyp));