--- a/moz.configure
+++ b/moz.configure
@@ -316,17 +316,17 @@ def makensis_progs(target):
     # We use an absolute path and insert as the first entry so it is preferred
     # over a 64-bit exe that may be in PATH.
     if 'MSYSTEM_PREFIX' in os.environ:
         prefix = os.path.dirname(os.environ['MSYSTEM_PREFIX'])
         candidates.insert(0, os.path.join(prefix, 'mingw32', 'bin', 'makensis.exe'))
 
     return tuple(candidates)
 
-nsis = check_prog('MAKENSISU', makensis_progs)
+nsis = check_prog('MAKENSISU', makensis_progs, allow_missing=True)
 
 # Make sure the version of makensis is up to date.
 @depends_if(nsis)
 @checking('for NSIS version')
 @imports('re')
 def nsis_version(nsis):
     nsis_min_version = '3.0b1'
     out = check_cmd_output(nsis, '-version',