Unable to use sqr

[tbhaxor]

In DrRacket i am using (sqr 3) its showing 9 i.e running perfectly. But in notebook as soon as execute the block it says

sqr: undefined;
 cannot reference an identifier before its definition
  in module: top-level
  context...:
   eval-one-top12
   /usr/share/racket/pkgs/sandbox-lib/racket/sandbox.rkt:510:0: call-with-custodian-shutdown
   /usr/share/racket/collects/racket/private/more-scheme.rkt:148:2: call-with-break-parameterization
   .../more-scheme.rkt:261:28
   /usr/share/racket/pkgs/sandbox-lib/racket/sandbox.rkt:878:5: loop