diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index 0919cbe1c..373de8d5a 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -255,7 +255,7 @@ int ecp_group_read_string( ecp_group *grp, int radix,
  *                  or POLARSSL_ERR_ECP_BUFFER_TOO_SMALL
  */
 int ecp_point_write_binary( const ecp_group *grp, const ecp_point *P,
-                            int format, uint8_t *olen,
+                            int format, size_t *olen,
                             unsigned char *buf, size_t buflen );
 
 /**
@@ -348,7 +348,8 @@ int ecp_tls_read_point( const ecp_group *grp, ecp_point *pt,
  *                  or POLARSSL_ERR_ECP_BUFFER_TOO_SMALL
  */
 int ecp_tls_write_point( const ecp_group *grp, const ecp_point *pt,
-                         int format, unsigned char *buf, size_t buf_len );
+                         int format, size_t *olen,
+                         unsigned char *buf, size_t blen );
 
 /**
  * \brief           Addition: R = P + Q
diff --git a/library/ecp.c b/library/ecp.c
index 41fc9dbac..233c2eba4 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -186,7 +186,7 @@ cleanup:
  * Export a point into unsigned binary data (SEC1 2.3.3)
  */
 int ecp_point_write_binary( const ecp_group *grp, const ecp_point *P,
-                            int format, uint8_t *olen,
+                            int format, size_t *olen,
                             unsigned char *buf, size_t buflen )
 {
     int ret;
@@ -293,15 +293,28 @@ int ecp_tls_read_point( const ecp_group *grp, ecp_point *pt,
  *      } ECPoint;
  */
 int ecp_tls_write_point( const ecp_group *grp, const ecp_point *pt,
-                         int format, unsigned char *buf, size_t buf_len )
+                         int format, size_t *olen,
+                         unsigned char *buf, size_t blen )
 {
+    int ret;
+
     /*
-     * buf_len must be at least one, for our length byte
+     * buffer length must be at least one, for our length byte
      */
-    if( buf_len < 1 )
+    if( blen < 1 )
         return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
 
-    return ecp_point_write_binary( grp, pt, format, buf, buf + 1, buf_len - 1);
+    if( ( ret = ecp_point_write_binary( grp, pt, format,
+                    olen, buf + 1, blen - 1) ) != 0 )
+        return( ret );
+
+    /*
+     * write length to the first byte and update total length
+     */
+    buf[0] = *olen;
+    ++*olen;
+
+    return 0;
 }
 
 /*
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index d07531c97..bf6104e57 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -230,7 +230,7 @@ ecp_write_binary:id:x:y:z:format:out:blen:ret
     ecp_group grp;
     ecp_point P;
     unsigned char buf[256], str[512];
-    uint8_t olen;
+    size_t olen;
 
     memset( buf, 0, sizeof( buf ) );
     memset( str, 0, sizeof( str ) );
@@ -299,6 +299,7 @@ ecp_tls_write_read_point:id
     ecp_group grp;
     ecp_point pt;
     unsigned char buf[256];
+    size_t olen;
 
     ecp_group_init( &grp );
     ecp_point_init( &pt );
@@ -307,27 +308,27 @@ ecp_tls_write_read_point:id
     TEST_ASSERT( ecp_use_known_dp( &grp, POLARSSL_ECP_DP_{id} ) == 0 );
 
     TEST_ASSERT( ecp_tls_write_point( &grp, &grp.G,
-                    POLARSSL_ECP_PF_COMPRESSED, buf, 256 ) == 0 );
-    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, 256 )
+                    POLARSSL_ECP_PF_COMPRESSED, &olen, buf, 256 ) == 0 );
+    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, olen )
                  == POLARSSL_ERR_ECP_BAD_INPUT_DATA );
 
     TEST_ASSERT( ecp_tls_write_point( &grp, &grp.G,
-                    POLARSSL_ECP_PF_UNCOMPRESSED, buf, 256 ) == 0 );
-    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, 256 ) == 0 );
+                    POLARSSL_ECP_PF_UNCOMPRESSED, &olen, buf, 256 ) == 0 );
+    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, olen ) == 0 );
     TEST_ASSERT( mpi_cmp_mpi( &grp.G.X, &pt.X ) == 0 );
     TEST_ASSERT( mpi_cmp_mpi( &grp.G.Y, &pt.Y ) == 0 );
     TEST_ASSERT( mpi_cmp_mpi( &grp.G.Z, &pt.Z ) == 0 );
 
     TEST_ASSERT( ecp_set_zero( &pt ) == 0 );
     TEST_ASSERT( ecp_tls_write_point( &grp, &pt,
-                    POLARSSL_ECP_PF_COMPRESSED, buf, 256 ) == 0 );
-    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, 256 ) == 0 );
+                    POLARSSL_ECP_PF_COMPRESSED, &olen, buf, 256 ) == 0 );
+    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, olen ) == 0 );
     TEST_ASSERT( ecp_is_zero( &pt ) );
 
     TEST_ASSERT( ecp_set_zero( &pt ) == 0 );
     TEST_ASSERT( ecp_tls_write_point( &grp, &pt,
-                    POLARSSL_ECP_PF_UNCOMPRESSED, buf, 256 ) == 0 );
-    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, 256 ) == 0 );
+                    POLARSSL_ECP_PF_UNCOMPRESSED, &olen, buf, 256 ) == 0 );
+    TEST_ASSERT( ecp_tls_read_point( &grp, &pt, buf, olen ) == 0 );
     TEST_ASSERT( ecp_is_zero( &pt ) );
 
     ecp_group_free( &grp );