diff --git a/kokoro/cmake.sh b/kokoro/cmake.sh
index 0cb79f5..f3db5bc 100755
--- a/kokoro/cmake.sh
+++ b/kokoro/cmake.sh
@@ -8,6 +8,8 @@
     CMAKE_G_A_FLAGS=('-G' 'Visual Studio 14 2015' '-A' 'x64')
     ;;
   *)
+    # Work around a bug in older versions of bash. :/
+    set +u
     CMAKE_G_A_FLAGS=()
     ;;
 esac