diff --git a/configure/os/CONFIG.Common.hpux-parisc b/configure/os/CONFIG.Common.hpux-parisc
index f8c43c568..db619932d 100644
--- a/configure/os/CONFIG.Common.hpux-parisc
+++ b/configure/os/CONFIG.Common.hpux-parisc
@@ -13,7 +13,7 @@ include $(CONFIG)/os/CONFIG.Common.UnixCommon
 OS_CLASS = hpux
 ARCH_CLASS = parisc
 
-POSIX_CPPFLAGS_YES =
+POSIX_CPPFLAGS_YES = -D_POSIX_C_SOURCE=199506L
 POSIX_CPPFLAGS_NO =
 POSIX_LDLIBS_YES +=
 POSIX_LDLIBS_NO +=