diff --git a/sherpa-onnx/c-api/c-api.cc b/sherpa-onnx/c-api/c-api.cc
index f6160deb1..eaf782b92 100644
--- a/sherpa-onnx/c-api/c-api.cc
+++ b/sherpa-onnx/c-api/c-api.cc
@@ -79,6 +79,10 @@ SherpaOnnxOnlineRecognizer *CreateOnlineRecognizer(
       SHERPA_ONNX_OR(config->model_config.model_type, "");
   recognizer_config.model_config.debug =
       SHERPA_ONNX_OR(config->model_config.debug, 0);
+  recognizer_config.model_config.modeling_unit =
+      SHERPA_ONNX_OR(config->model_config.modeling_unit, "cjkchar");
+  recognizer_config.model_config.bpe_vocab =
+      SHERPA_ONNX_OR(config->model_config.bpe_vocab, "");
 
   recognizer_config.decoding_method =
       SHERPA_ONNX_OR(config->decoding_method, "greedy_search");
@@ -357,6 +361,10 @@ SherpaOnnxOfflineRecognizer *CreateOfflineRecognizer(
       SHERPA_ONNX_OR(config->model_config.provider, "cpu");
   recognizer_config.model_config.model_type =
       SHERPA_ONNX_OR(config->model_config.model_type, "");
+  recognizer_config.model_config.modeling_unit =
+      SHERPA_ONNX_OR(config->model_config.modeling_unit, "cjkchar");
+  recognizer_config.model_config.bpe_vocab =
+      SHERPA_ONNX_OR(config->model_config.bpe_vocab, "");
 
   recognizer_config.lm_config.model =
       SHERPA_ONNX_OR(config->lm_config.model, "");
diff --git a/sherpa-onnx/c-api/c-api.h b/sherpa-onnx/c-api/c-api.h
index 1b1b56330..bd9b6a4d4 100644
--- a/sherpa-onnx/c-api/c-api.h
+++ b/sherpa-onnx/c-api/c-api.h
@@ -82,6 +82,12 @@ SHERPA_ONNX_API typedef struct SherpaOnnxOnlineModelConfig {
   const char *provider;
   int32_t debug;  // true to print debug information of the model
   const char *model_type;
+  // Valid values:
+  //  - cjkchar
+  //  - bpe
+  //  - cjkchar+bpe
+  const char *modeling_unit;
+  const char *bpe_vocab;
 } SherpaOnnxOnlineModelConfig;
 
 /// It expects 16 kHz 16-bit single channel wave format.
@@ -383,6 +389,12 @@ SHERPA_ONNX_API typedef struct SherpaOnnxOfflineModelConfig {
   int32_t debug;
   const char *provider;
   const char *model_type;
+  // Valid values:
+  //  - cjkchar
+  //  - bpe
+  //  - cjkchar+bpe
+  const char *modeling_unit;
+  const char *bpe_vocab;
 } SherpaOnnxOfflineModelConfig;
 
 SHERPA_ONNX_API typedef struct SherpaOnnxOfflineRecognizerConfig {