diff --git a/runtime/tools/lib/LibOMP.pm b/runtime/tools/lib/LibOMP.pm
index 497b926..cff7e4a 100644
--- a/runtime/tools/lib/LibOMP.pm
+++ b/runtime/tools/lib/LibOMP.pm
@@ -16,7 +16,7 @@
 
 sub empty($) {
     my ( $var ) = @_;
-    return (not exists($ENV{$var})) or (not defined($ENV{$var})) or ($ENV{$var} eq "");
+    return ((not exists($ENV{$var})) or (not defined($ENV{$var})) or ($ENV{$var} eq ""));
 }; # sub empty
 
 my ( $base, $out, $tmp );