diff --git a/library/oid.c b/library/oid.c
index 366720e..750ece8 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -591,8 +591,7 @@
     for( i = 1; i < oid->len; i++ )
     {
         /* Prevent overflow in value. */
-        unsigned int v = value << 7;
-        if ( v < value )
+        if ( ( ( value << 7 ) >> 7 ) != value )
             return( POLARSSL_ERR_DEBUG_BUF_TOO_SMALL );
 
         value <<= 7;