diff --git a/configure.ac b/configure.ac
index 7df6627a..d926c8f2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -378,7 +378,7 @@ 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"