diff --git a/package/libmicrohttpd/libmicrohttpd.mk b/package/libmicrohttpd/libmicrohttpd.mk
index f75178bc0a..344e1443fd 100644
--- a/package/libmicrohttpd/libmicrohttpd.mk
+++ b/package/libmicrohttpd/libmicrohttpd.mk
@@ -12,6 +12,10 @@ LIBMICROHTTPD_INSTALL_STAGING = YES
 LIBMICROHTTPD_CONF_OPTS = --disable-curl --disable-examples
 LIBMICROHTTPD_CFLAGS = $(TARGET_CFLAGS) -std=c99
 
+ifeq ($(BR2_TOOLCHAIN_HAS_THREADS),y)
+LIBMICROHTTPD_CFLAGS += -D_REENTRANT
+endif
+
 LIBMICROHTTPD_CONF_ENV += CFLAGS="$(LIBMICROHTTPD_CFLAGS)"
 
 ifeq ($(BR2_PACKAGE_LIBMICROHTTPD_SSL),y)