diff --git a/racket/src/cs/primitive/flfxnum.ss b/racket/src/cs/primitive/flfxnum.ss
index 0e358fbfaf..47c867163d 100644
--- a/racket/src/cs/primitive/flfxnum.ss
+++ b/racket/src/cs/primitive/flfxnum.ss
@@ -52,15 +52,15 @@
   [fxabs (known-procedure/folding/limited 2 'fixnum)]
   [fxand (known-procedure/folding/limited -1 'fixnum)]
   [fxior (known-procedure/folding/limited -1 'fixnum)]
-  [fxlshift (known-procedure/folding/limited 4 'fixnum)]
-  [fxlshift/wraparound (known-procedure/folding/limited 4 'fixnum)]
+  [fxlshift (known-procedure/has-unsafe/folding/limited 4 'unsafe-fxlshift 'fixnum)]
+  [fxlshift/wraparound (known-procedure/has-unsafe/folding/limited 4 'unsafe-fxlshift/wraparound 'fixnum)]
   [fxmax (known-procedure/folding/limited -2 'fixnum)]
   [fxmin (known-procedure/folding/limited -2 'fixnum)]
   [fxmodulo (known-procedure/folding/limited 4 'fixnum)]
   [fxnot (known-procedure/folding/limited 2 'fixnum)]
   [fxquotient (known-procedure/folding/limited 4 'fixnum)]
   [fxremainder (known-procedure/folding/limited 4 'fixnum)]
-  [fxrshift (known-procedure/folding/limited 4 'fixnum)]
+  [fxrshift (known-procedure/has-unsafe/folding/limited 4 'unsafe-fxrshift 'fixnum)]
   [fxvector (known-procedure/single-valued -1)]
   [fxvector-length (known-procedure/folding/limited 2 'fixnum)]
   [fxvector-ref (known-procedure/folding/limited 4 'fixnum)]