diff --git a/library/ecp.c b/library/ecp.c
index 7cfb44f..d742e81 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -483,8 +483,13 @@
     int ret;
     size_t plen;
 
-    if( ilen == 1 && buf[0] == 0x00 )
-        return( ecp_set_zero( pt ) );
+    if( buf[0] == 0x00 )
+    {
+        if( ilen == 1 )
+            return( ecp_set_zero( pt ) );
+        else
+            return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
+    }
 
     plen = mpi_size( &grp->P );