diff --git a/libs/pbd/wscript b/libs/pbd/wscript
index 32ce830306..729aa7ead1 100644
--- a/libs/pbd/wscript
+++ b/libs/pbd/wscript
@@ -39,10 +39,10 @@ def configure(conf):
     if sys.platform != 'darwin':
         autowaf.check_pkg(conf, 'uuid', uselib_store='UUID')
 
-    conf.check(function_name='getmntent', header_name='mntent.h', define_name='HAVE_GETMNTENT')
-    conf.check(header_name='execinfo.h', define_name='HAVE_EXECINFO')
-    conf.check(header_name='unistd.h', define_name='HAVE_UNISTD')
-    if conf.check_cc(function_name='posix_memalign', header_name='stdlib.h', cflags='-D_XOPEN_SOURCE=600') == False:
+    conf.check(function_name='getmntent', header_name='mntent.h', define_name='HAVE_GETMNTENT',mandatory=False)
+    conf.check(header_name='execinfo.h', define_name='HAVE_EXECINFO',mandatory=False)
+    conf.check(header_name='unistd.h', define_name='HAVE_UNISTD',mandatory=False)
+    if conf.check_cc(function_name='posix_memalign', header_name='stdlib.h', cflags='-D_XOPEN_SOURCE=600',mandatory=False) == False:
         conf.define ('NO_POSIX_MEMALIGN',1)
 
     conf.write_config_header('libpbd-config.h', remove=False)