diff --git a/tests/factor/factor.pl b/tests/factor/factor.pl
index 8f4963530..7def27c52 100755
--- a/tests/factor/factor.pl
+++ b/tests/factor/factor.pl
@@ -92,7 +92,7 @@ my @Tests =
       {ERR => ("$prog: '340282366920938463463374607431768211456a'"
                . " is not a valid positive integer\n")}],
      ['bug-gmp-2_sup_128-suffix-space',
-      '340282366920938463463374607431768211456 ',
+      "'340282366920938463463374607431768211456 '",
       {EXIT => 1},
       {ERR => ("$prog: '340282366920938463463374607431768211456 '"
                . " is not a valid positive integer\n")}],