diff --git a/tools/distrib/build_ruby_environment_macos.sh b/tools/distrib/build_ruby_environment_macos.sh
index a876990b985d6bff9a5562a3e07f0745f60a8214..b6dec68c7fc70fe416decf15203c6fbc24b6ace3 100644
--- a/tools/distrib/build_ruby_environment_macos.sh
+++ b/tools/distrib/build_ruby_environment_macos.sh
@@ -30,7 +30,7 @@
 
 set -ex
 
-CROSS_RUBY=`mktemp`
+CROSS_RUBY=`mktemp tmpfile.XXXXXXXX`
 
 curl https://raw.githubusercontent.com/rake-compiler/rake-compiler/v0.9.5/tasks/bin/cross-ruby.rake > $CROSS_RUBY