diff --git a/build.sh b/build.sh
index 4cda74badf..490c9ac02a 100755
--- a/build.sh
+++ b/build.sh
@@ -628,6 +628,8 @@ set_boot_image_vars() {
         CHECKSUM_URL="$url"
         BOOT_IMAGE_URL="http://downloads.factorcode.org/images/${CURRENT_BRANCH}/${BOOT_IMAGE}"
     else
+        $ECHO "boot image for branch \`${CURRENT_BRANCH}\` is not on server, trying master instead"
+        $ECHO "  tried nonexistent url: ${url}"
         CHECKSUM_URL="http://downloads.factorcode.org/images/master/checksums.txt"
         BOOT_IMAGE_URL="http://downloads.factorcode.org/images/master/${BOOT_IMAGE}"
     fi