diff --git a/src/speak_lib.h b/src/speak_lib.h
index a5b2604c..65d153c1 100644
--- a/src/speak_lib.h
+++ b/src/speak_lib.h
@@ -484,13 +484,15 @@ ESPEAK_API void espeak_SetPhonemeTrace(int value, FILE *stream);
 #ifdef __cplusplus
 extern "C"
 #endif
-ESPEAK_API void espeak_TextToPhonemes(const void *text, char *buffer, int size, int textmode, int phonememode);
+ESPEAK_API const char *espeak_TextToPhonemes(const void **textptr, int textmode, int phonememode);
 /* Translates text into phonemes.  Call espeak_SetVoiceByName() first, to select a language.
-   text: The text to translate, terminated by a zero character.
 
-   buffer: Output buffer for the phoneme translation.
+   It returns a pointer to a character string which contains the phonemes for the text up to
+   end of a sentence, or comma, semicolon, colon, or similar punctuation.
 
-   size: Size of the output buffer in bytes.
+   textptr: The address of a pointer to the input text which is terminated by a zero character.
+      On return, the pointer has been advanced past the text which has been translated, or else set
+      to NULL to indicate that the end of the text has been reached.
 
    textmode: Type of character codes, one of:
          espeakCHARS_UTF8     UTF8 encoding