diff --git a/build-book-converter.jenkins b/build-book-converter.jenkins
index 768700b..8f2a74c 100644
--- a/build-book-converter.jenkins
+++ b/build-book-converter.jenkins
@@ -52,8 +52,8 @@ IFS=\$'\\n'
 
 while true; do
         sleep 5s
-        if [ -z "\$(find /calibre/input -type f \\( -iname \\*.mobi -o -iname \\*.epub -o \\*.prc \\) -print -quit)" ]; then
-                for i in \$(find /calibre/input -type f \\( -iname \\*.mobi -o -iname \\*.epub -o \\*.prc \\)); do
+        if [ -z "\$(find /calibre/input -type f \\( -iname "*.mobi" -o -iname "*.epub" -o -iname "*.prc" \\) -print -quit)" ]; then
+                for i in \$(find /calibre/input -type f \\( -iname "*.mobi" -o -iname "*.epub" -o -iname "*.prc" \\)); do
                         /opt/calibre/ebook-convert "\${i}" "/calibre/output/\${i%.*}.azw3"
                         rm -f -v "\${i}"
                 done