diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index ef99351..094a840 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -412,7 +412,7 @@
  *
  * \note            buf is updated to point right after the ECPoint on exit
  *
- * \return          O if successful,
+ * \return          0 if successful,
  *                  POLARSSL_ERR_MPI_XXX if initialization failed
  *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if input is invalid
  */
@@ -462,7 +462,7 @@
  * \param grp       Destination group
  * \param index     Index in the list of well-known domain parameters
  *
- * \return          O if successful,
+ * \return          0 if successful,
  *                  POLARSSL_ERR_MPI_XXX if initialization failed
  *                  POLARSSL_ERR_ECP_FEATURE_UNAVAILABLE for unkownn groups
  *
@@ -480,7 +480,7 @@
  *
  * \note            buf is updated to point right after ECParameters on exit
  *
- * \return          O if successful,
+ * \return          0 if successful,
  *                  POLARSSL_ERR_MPI_XXX if initialization failed
  *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if input is invalid
  */