diff --git a/mozilla/modules/security/freenav/Makefile.in b/mozilla/modules/security/freenav/Makefile.in
index a16478bed6a..22b7ea747cd 100644
--- a/mozilla/modules/security/freenav/Makefile.in
+++ b/mozilla/modules/security/freenav/Makefile.in
@@ -56,4 +56,8 @@ REQUIRES		= js img layer util
 
 include $(topsrcdir)/config/rules.mk
 
+ifeq ($(OS_ARCH), Linux)
+DEFINES += -D_BSD_SOURCE
+endif
+
 $(LIBRARY): $(OBJS)