diff --git a/libs/fst/scanner.cc b/libs/fst/scanner.cc
index f6478bcb5f..18f4048cbb 100644
--- a/libs/fst/scanner.cc
+++ b/libs/fst/scanner.cc
@@ -1,4 +1,3 @@
-#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/libs/fst/wscript b/libs/fst/wscript
index 465ba65840..ca90b7207d 100644
--- a/libs/fst/wscript
+++ b/libs/fst/wscript
@@ -88,7 +88,7 @@ def build(bld):
         'PACKAGE="' + I18N_PACKAGE + str(bld.env['MAJOR']) + '"',
         'LIBARDOUR="' + bld.env['lwrcase_dirname'] + '"',
         ]
-    if re.search ("freebsd", sys.platform) != None:
+    if re.search ("freebsd", sys.platform) != None or re.search ("openbsd", sys.platform) != None:
         obj.defines.append('_POSIX_C_SOURCE=200809')
         obj.defines.append('_XOPEN_SOURCE=700')