diff --git a/CMakeLists.txt b/CMakeLists.txt
index 183278d1a..a449b3532 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -20,7 +20,7 @@ option(SHERPA_ONNX_ENABLE_JNI "Whether to build JNI internface" OFF)
 option(SHERPA_ONNX_ENABLE_C_API "Whether to build C API" ON)
 option(SHERPA_ONNX_ENABLE_WEBSOCKET "Whether to build webscoket server/client" ON)
 option(SHERPA_ONNX_ENABLE_GPU "Enable ONNX Runtime GPU support" OFF)
-option(SHERPA_ONNX_LINK_LIBSTDCPP_STATICALLY "True to link libstdc++ statically. Used only when BUILD_SHARED_LIBS is ON on Linux" ON)
+option(SHERPA_ONNX_LINK_LIBSTDCPP_STATICALLY "True to link libstdc++ statically. Used only when BUILD_SHARED_LIBS is OFF on Linux" ON)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
diff --git a/python-api-examples/offline-tts.py b/python-api-examples/offline-tts.py
index f36ea6f49..630454d71 100755
--- a/python-api-examples/offline-tts.py
+++ b/python-api-examples/offline-tts.py
@@ -124,6 +124,11 @@ def main():
     start = time.time()
     audio = tts.generate(args.text, sid=args.sid)
     end = time.time()
+
+    if len(audio.samples) == 0:
+        print("Error in generating audios. Please read previous error messages.")
+        return
+
     elapsed_seconds = end - start
     audio_duration = len(audio.samples) / audio.sample_rate
     real_time_factor = elapsed_seconds / audio_duration
diff --git a/sherpa-onnx/csrc/lexicon.cc b/sherpa-onnx/csrc/lexicon.cc
index 3707f1489..87203f4e1 100644
--- a/sherpa-onnx/csrc/lexicon.cc
+++ b/sherpa-onnx/csrc/lexicon.cc
@@ -104,9 +104,17 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsChinese(
 
   std::vector<int64_t> ans;
 
-  ans.push_back(token2id_.at("sil"));
+  auto sil = token2id_.at("sil");
+  auto eos = token2id_.at("eos");
+
+  ans.push_back(sil);
 
   for (const auto &w : words) {
+    if (punctuations_.count(w)) {
+      ans.push_back(sil);
+      continue;
+    }
+
     if (!word2ids_.count(w)) {
       SHERPA_ONNX_LOGE("OOV %s. Ignore it!", w.c_str());
       continue;
@@ -115,8 +123,8 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsChinese(
     const auto &token_ids = word2ids_.at(w);
     ans.insert(ans.end(), token_ids.begin(), token_ids.end());
   }
-  ans.push_back(token2id_.at("sil"));
-  ans.push_back(token2id_.at("eos"));
+  ans.push_back(sil);
+  ans.push_back(eos);
   return ans;
 }
 
@@ -126,6 +134,7 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
   ToLowerCase(&text);
 
   std::vector<std::string> words = SplitUtf8(text);
+  int32_t blank = token2id_.at(" ");
 
   std::vector<int64_t> ans;
   for (const auto &w : words) {
@@ -141,12 +150,10 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
 
     const auto &token_ids = word2ids_.at(w);
     ans.insert(ans.end(), token_ids.begin(), token_ids.end());
-    if (blank_ != -1) {
-      ans.push_back(blank_);
-    }
+    ans.push_back(blank);
   }
 
-  if (blank_ != -1 && !ans.empty()) {
+  if (!ans.empty()) {
     // remove the last blank
     ans.resize(ans.size() - 1);
   }
@@ -156,9 +163,6 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
 
 void Lexicon::InitTokens(const std::string &tokens) {
   token2id_ = ReadTokens(tokens);
-  if (token2id_.count(" ")) {
-    blank_ = token2id_.at(" ");
-  }
 }
 
 void Lexicon::InitLanguage(const std::string &_lang) {
diff --git a/sherpa-onnx/csrc/lexicon.h b/sherpa-onnx/csrc/lexicon.h
index 74e374ee1..35bace8f8 100644
--- a/sherpa-onnx/csrc/lexicon.h
+++ b/sherpa-onnx/csrc/lexicon.h
@@ -44,7 +44,6 @@ class Lexicon {
   std::unordered_map<std::string, std::vector<int32_t>> word2ids_;
   std::unordered_set<std::string> punctuations_;
   std::unordered_map<std::string, int32_t> token2id_;
-  int32_t blank_ = -1;  // ID for the blank token
   Language language_;
   //
 };
diff --git a/sherpa-onnx/csrc/offline-tts-vits-impl.h b/sherpa-onnx/csrc/offline-tts-vits-impl.h
index 7174e78cd..b553ebe4a 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-impl.h
+++ b/sherpa-onnx/csrc/offline-tts-vits-impl.h
@@ -25,6 +25,23 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
 
   GeneratedAudio Generate(const std::string &text,
                           int64_t sid = 0) const override {
+    int32_t num_speakers = model_->NumSpeakers();
+    if (num_speakers == 0 && sid != 0) {
+      SHERPA_ONNX_LOGE(
+          "This is a single-speaker model and supports only sid 0. Given sid: "
+          "%d",
+          sid);
+      return {};
+    }
+
+    if (num_speakers != 0 && (sid >= num_speakers || sid < 0)) {
+      SHERPA_ONNX_LOGE(
+          "This model contains only %d speakers. sid should be in the range "
+          "[%d, %d]. Given: %d",
+          num_speakers, 0, num_speakers - 1, sid);
+      return {};
+    }
+
     std::vector<int64_t> x = lexicon_.ConvertTextToTokenIds(text);
     if (x.empty()) {
       SHERPA_ONNX_LOGE("Failed to convert %s to token IDs", text.c_str());
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model.cc b/sherpa-onnx/csrc/offline-tts-vits-model.cc
index 06aab516f..4f2ae9ec0 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model.cc
+++ b/sherpa-onnx/csrc/offline-tts-vits-model.cc
@@ -85,6 +85,7 @@ class OfflineTtsVitsModel::Impl {
 
   std::string Punctuations() const { return punctuations_; }
   std::string Language() const { return language_; }
+  int32_t NumSpeakers() const { return num_speakers_; }
 
  private:
   void Init(void *model_data, size_t model_data_length) {
@@ -107,7 +108,7 @@ class OfflineTtsVitsModel::Impl {
     Ort::AllocatorWithDefaultOptions allocator;  // used in the macro below
     SHERPA_ONNX_READ_META_DATA(sample_rate_, "sample_rate");
     SHERPA_ONNX_READ_META_DATA(add_blank_, "add_blank");
-    SHERPA_ONNX_READ_META_DATA(n_speakers_, "n_speakers");
+    SHERPA_ONNX_READ_META_DATA(num_speakers_, "n_speakers");
     SHERPA_ONNX_READ_META_DATA_STR(punctuations_, "punctuation");
     SHERPA_ONNX_READ_META_DATA_STR(language_, "language");
   }
@@ -128,7 +129,7 @@ class OfflineTtsVitsModel::Impl {
 
   int32_t sample_rate_;
   int32_t add_blank_;
-  int32_t n_speakers_;
+  int32_t num_speakers_;
   std::string punctuations_;
   std::string language_;
 };
@@ -152,4 +153,8 @@ std::string OfflineTtsVitsModel::Punctuations() const {
 
 std::string OfflineTtsVitsModel::Language() const { return impl_->Language(); }
 
+int32_t OfflineTtsVitsModel::NumSpeakers() const {
+  return impl_->NumSpeakers();
+}
+
 }  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model.h b/sherpa-onnx/csrc/offline-tts-vits-model.h
index 0c8208d53..a3870fbd7 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model.h
+++ b/sherpa-onnx/csrc/offline-tts-vits-model.h
@@ -39,6 +39,7 @@ class OfflineTtsVitsModel {
 
   std::string Punctuations() const;
   std::string Language() const;
+  int32_t NumSpeakers() const;
 
  private:
   class Impl;
diff --git a/sherpa-onnx/csrc/sherpa-onnx-offline-tts.cc b/sherpa-onnx/csrc/sherpa-onnx-offline-tts.cc
index bd4fc4e00..6097468a2 100644
--- a/sherpa-onnx/csrc/sherpa-onnx-offline-tts.cc
+++ b/sherpa-onnx/csrc/sherpa-onnx-offline-tts.cc
@@ -81,6 +81,12 @@ or detailes.
 
   sherpa_onnx::OfflineTts tts(config);
   auto audio = tts.Generate(po.GetArg(1), sid);
+  if (audio.samples.empty()) {
+    fprintf(
+        stderr,
+        "Error in generating audios. Please read previous error messages.\n");
+    exit(EXIT_FAILURE);
+  }
 
   bool ok = sherpa_onnx::WriteWave(output_filename, audio.sample_rate,
                                    audio.samples.data(), audio.samples.size());