diff --git a/package/tor/tor.mk b/package/tor/tor.mk
index 9cca011228..f6d3b7fe25 100644
--- a/package/tor/tor.mk
+++ b/package/tor/tor.mk
@@ -32,4 +32,6 @@ else
 TOR_CONF_OPTS += --disable-seccomp
 endif
 
+TOR_CONF_ENV = ac_cv_prog_cc_c99='-std=gnu99'
+
 $(eval $(autotools-package))