diff --git a/src/datax_stl/stl_io.h b/src/datax_stl/stl_io.h
index ff0dbda..4831dda 100644
--- a/src/datax_stl/stl_io.h
+++ b/src/datax_stl/stl_io.h
@@ -19,7 +19,7 @@ FOUG_DATAX_LIBSTL_EXPORT int foug_stla_read(foug_stl_geom_creator_t* creator,
                                             size_t                   data_size_hint);
 
 /*! Write geometry in the STL ascii format */
-FOUG_DATAX_LIBSTL_EXPORT int foug_stla_write(foug_stl_geom_t* geom,
+FOUG_DATAX_LIBSTL_EXPORT int foug_stla_write(const foug_stl_geom_t* geom,
                                              foug_transfer_t* trsf,
                                              const char*      solid_name,
                                              uint8_t          real32_prec);
diff --git a/src/datax_stl/stla_write.c b/src/datax_stl/stla_write.c
index 936163e..44e79cc 100644
--- a/src/datax_stl/stla_write.c
+++ b/src/datax_stl/stla_write.c
@@ -100,14 +100,14 @@ static foug_bool_t foug_transfer_flush_buffer(foug_transfer_t* trsf, size_t n)
  *
  *  \param geom Defines the custom geometry to write
  *  \param trsf Defines needed objects (stream, buffer, ...) for the writing operation
-*   \param solid_name May be NULL to generate default name
+ *  \param solid_name May be NULL to generate default name
  *  \param real32_prec The maximum number of significant digits
  *
  *  \return Error code
  *
  *  \retval FOUG_DATAX_NO_ERROR If operation successful
  */
-int foug_stla_write(foug_stl_geom_t* geom,
+int foug_stla_write(const foug_stl_geom_t* geom,
                     foug_transfer_t* trsf,
                     const char* solid_name,
                     uint8_t real32_prec)