diff --git a/crew b/crew
index 8612a3f1b..64f84c801 100755
--- a/crew
+++ b/crew
@@ -37,6 +37,14 @@ Usage:
 version 0.4.3
 DOCOPT
 
+# Set XZ_OPT environment variable for build command.
+# If CREW_XZ_OPT is defined, use it by default.  Use `-7e`, otherwise.
+if ENV["CREW_XZ_OPT"].to_s == ''
+  ENV["XZ_OPT"] = "-7e -T #{CREW_NPROC}"
+else
+  ENV["XZ_OPT"] = ENV["CREW_XZ_OPT"]
+end
+
 # Parse arguments using docopt
 require_relative 'lib/docopt'
 begin
diff --git a/lib/const.rb b/lib/const.rb
index cb7971f6d..0c80bd865 100644
--- a/lib/const.rb
+++ b/lib/const.rb
@@ -26,12 +26,4 @@ CREW_NOT_COMPRESS = ENV["CREW_NOT_COMPRESS"]
 # Set CREW_NOT_STRIP from environment variable
 CREW_NOT_STRIP = ENV["CREW_NOT_STRIP"]
 
-# Set XZ_OPT environment variable for build command.
-# If CREW_XZ_OPT is defined, use it by default.  Use `-7e`, otherwise.
-if ENV["CREW_XZ_OPT"].to_s == ''
-  ENV["XZ_OPT"] = "-7e"
-else
-  ENV["XZ_OPT"] = ENV["CREW_XZ_OPT"]
-end
-
 USER = `whoami`.chomp