Retry brew update if it fails
diff --git a/.travis/install.sh b/.travis/install.sh
index 9e14a92..57ece2e 100755
--- a/.travis/install.sh
+++ b/.travis/install.sh
@@ -4,7 +4,7 @@
 set -x
 
 if [[ "$(uname -s)" == 'Darwin' ]]; then
-    brew update
+    brew update || brew update
 
     if [[ "${OPENSSL}" != "0.9.8" ]]; then
         brew upgrade openssl