diff --git a/.gitignore b/.gitignore
index 53bddb47e..28bf143ce 100644
--- a/.gitignore
+++ b/.gitignore
@@ -134,3 +134,5 @@ us_gold.json
 us_silver.json
 kokoro-multi-lang-v1_0
 sherpa-onnx-fire-red-asr-large-zh_en-2025-02-16
+cmake-build-debug
+README-DEV.txt
diff --git a/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h b/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
index fc6cc74ed..605d864b4 100644
--- a/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
+++ b/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
@@ -23,28 +23,6 @@
 
 namespace sherpa_onnx {
 
-static OfflineRecognitionResult Convert(const OfflineWhisperDecoderResult &src,
-                                        const SymbolTable &sym_table) {
-  OfflineRecognitionResult r;
-  r.tokens.reserve(src.tokens.size());
-
-  std::string text;
-  for (auto i : src.tokens) {
-    if (!sym_table.Contains(i)) {
-      continue;
-    }
-
-    const auto &s = sym_table[i];
-    text += s;
-    r.tokens.push_back(s);
-  }
-
-  r.text = text;
-  r.lang = src.lang;
-
-  return r;
-}
-
 class OfflineRecognizerWhisperImpl : public OfflineRecognizerImpl {
  public:
   explicit OfflineRecognizerWhisperImpl(const OfflineRecognizerConfig &config)
@@ -156,7 +134,6 @@ class OfflineRecognizerWhisperImpl : public OfflineRecognizerImpl {
                                       std::move(cross_kv.second));
 
       auto r = Convert(results[0], symbol_table_);
-      r.text = ApplyInverseTextNormalization(std::move(r.text));
       s->SetResult(r);
     } catch (const Ort::Exception &ex) {
       SHERPA_ONNX_LOGE(
@@ -169,6 +146,31 @@ class OfflineRecognizerWhisperImpl : public OfflineRecognizerImpl {
     }
   }
 
+ private:
+  OfflineRecognitionResult Convert(const OfflineWhisperDecoderResult &src,
+                                   const SymbolTable &sym_table) const {
+    OfflineRecognitionResult r;
+    r.tokens.reserve(src.tokens.size());
+
+    std::string text;
+    for (auto i : src.tokens) {
+      if (!sym_table.Contains(i)) {
+        continue;
+      }
+
+      std::string s = sym_table[i];
+      s = ApplyInverseTextNormalization(s);
+
+      text += s;
+      r.tokens.push_back(s);
+    }
+
+    r.text = text;
+    r.lang = src.lang;
+
+    return r;
+  }
+
  private:
   OfflineRecognizerConfig config_;
   SymbolTable symbol_table_;
diff --git a/sherpa-onnx/csrc/text-utils-test.cc b/sherpa-onnx/csrc/text-utils-test.cc
index e9cee573f..c96280ada 100644
--- a/sherpa-onnx/csrc/text-utils-test.cc
+++ b/sherpa-onnx/csrc/text-utils-test.cc
@@ -55,4 +55,77 @@ TEST(RemoveInvalidUtf8Sequences, Case1) {
   EXPECT_EQ(s.size() + 4, v.size());
 }
 
+
+// Tests for sanitizeUtf8
+TEST(RemoveInvalidUtf8Sequences, ValidUtf8StringPassesUnchanged) {
+  std::string input = "Valid UTF-8 🌍";
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), input);
+}
+
+TEST(RemoveInvalidUtf8Sequences, SingleInvalidByteReplaced) {
+  std::string input = "Invalid \xFF UTF-8";
+  std::string expected = "Invalid  UTF-8";
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, TruncatedUtf8SequenceReplaced) {
+  std::string input = "Broken \xE2\x82";  // Incomplete UTF-8 sequence
+  std::string expected = "Broken ";
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, MultipleInvalidBytes) {
+  std::string input = "Test \xC0\xC0\xF8\xA0";  // Multiple invalid sequences
+  std::string expected = "Test ";
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, BreakingCase_SpaceFollowedByInvalidByte) {
+  std::string input = "\x20\xC4";  // Space followed by an invalid byte
+  std::string expected = " ";  // 0xC4 removed
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, ValidUtf8WithEdgeCaseCharacters) {
+  std::string input = "Edge 🏆💯";
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), input);
+}
+
+TEST(RemoveInvalidUtf8Sequences, MixedValidAndInvalidBytes) {
+  std::string input = "Mix \xE2\x82\xAC \xF0\x9F\x98\x81 \xFF";
+  std::string expected = "Mix € 😁 ";  // Invalid bytes removed
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, SpaceFollowedByInvalidByte) {
+  std::string input = "\x20\xC4";  // Space (0x20) followed by invalid (0xC4)
+  std::string expected = " ";  // Space remains, 0xC4 is removed
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, RemoveTruncatedC4) {
+  std::string input = "Hello \xc4 world";  // Invalid `0xC4`
+  std::string expected = "Hello  world";  // `0xC4` should be removed
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, SpaceFollowedByInvalidByte_Breaking) {
+  std::string input = "\x20\xc4";  // Space followed by invalid `0xc4`
+  std::string expected = " ";  // `0xc4` should be removed, space remains
+  EXPECT_EQ(RemoveInvalidUtf8Sequences(input), expected);
+}
+
+TEST(RemoveInvalidUtf8Sequences, DebugSpaceFollowedByInvalidByte) {
+  std::string input = "\x20\xc4";  // Space followed by invalid `0xc4`
+  std::string output = RemoveInvalidUtf8Sequences(input);
+
+  std::cout << "Processed string: ";
+  for (unsigned char c : output) {
+    printf("\\x%02x ", c);
+  }
+  std::cout << std::endl;
+
+  EXPECT_EQ(output, " ");  // Expect `0xc4` to be removed, leaving only space
+}
+
 }  // namespace sherpa_onnx