diff --git a/configure.ac b/configure.ac
index 104fd994..451eb622 100644
--- a/configure.ac
+++ b/configure.ac
@@ -384,7 +384,7 @@ case "${host}" in
 	abi="elf"
 	AC_DEFINE([JEMALLOC_PURGE_MADVISE_FREE], [ ])
 	;;
-  *-*-linux*)
+  *-*-linux* | *-*-kfreebsd*)
 	dnl syscall(2) and secure_getenv(3) are exposed by _GNU_SOURCE.
 	CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
 	abi="elf"