diff --git a/configure b/configure
index bf9d223c..be872caf 100755
--- a/configure
+++ b/configure
@@ -2447,7 +2447,8 @@ appendCXX "-D_FORTIFY_SOURCE=2"
 
 case "${host_os}" in
 	freebsd*)
-		appendCXX -I/usr/local/include
+		# -D__GNU_LIBRARY__ makes this work on fbsd 4.11
+		appendCXX -I/usr/local/include -D__GNU_LIBRARY__
 		appendLib -L/usr/local/lib -lcompat
 		appendMod -L/usr/local/lib
 	;;
diff --git a/configure.in b/configure.in
index 7371092c..9f39b636 100644
--- a/configure.in
+++ b/configure.in
@@ -44,7 +44,8 @@ appendCXX "-D_FORTIFY_SOURCE=2"
 
 case "${host_os}" in
 	freebsd*)
-		appendCXX -I/usr/local/include
+		# -D__GNU_LIBRARY__ makes this work on fbsd 4.11
+		appendCXX -I/usr/local/include -D__GNU_LIBRARY__
 		appendLib -L/usr/local/lib -lcompat
 		appendMod -L/usr/local/lib
 	;;