diff --git a/master.sh b/master.sh
index 039ce8a..ef42a09 100755
--- a/master.sh
+++ b/master.sh
@@ -540,7 +540,7 @@ get_book
 echo "${SD_BORDER}${nl_}"
 
 # If $BUILDDIR/sources hasn't been created yet at this point, create it.
-[[ -d $BUILDDIR/sources ]] && mkdir $BUILDDIR/sources
+[[ ! -d $BUILDDIR/sources ]] && mkdir $BUILDDIR/sources
 
 build_Makefile
 echo "${SD_BORDER}${nl_}"