include/apr.h.in |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/include/apr.h.in b/include/apr.h.in
index bef91eb..a27caf3 100644
--- a/include/apr.h.in
+++ b/include/apr.h.in
@@ -33,6 +33,10 @@
  * for Win32 or Netware by those build environments, respectively.
  */
 
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE 1
+#endif
+
 /**
  * @defgroup APR Apache Portability Runtime library
  * @{