diff --git a/src/sources/csv.lisp b/src/sources/csv.lisp
index 6b823f3..a54dc2a 100644
--- a/src/sources/csv.lisp
+++ b/src/sources/csv.lisp
@@ -46,8 +46,7 @@
 	     (pgloader.pgsql:list-columns (slot-value csv 'target-db)
 					  (slot-value csv 'target)))))
     (unless transforms
-      (setf (slot-value csv 'transforms)
-	    (loop for c in columns collect nil)))))
+      (setf (slot-value csv 'transforms) (make-list (length columns))))))
 
 ;;;
 ;;; Read a file format in CSV format, and call given function on each line.
diff --git a/src/sources/fixed.lisp b/src/sources/fixed.lisp
index 204d90a..95f4763 100644
--- a/src/sources/fixed.lisp
+++ b/src/sources/fixed.lisp
@@ -28,8 +28,7 @@
 	     (pgloader.pgsql:list-columns (slot-value fixed 'target-db)
 					  (slot-value fixed 'target)))))
     (unless transforms
-      (setf (slot-value fixed 'transforms)
-	    (loop :repeat (length columns) :collect nil)))))
+      (setf (slot-value fixed 'transforms) (make-list (length columns))))))
 
 (declaim (inline parse-row))
 
diff --git a/src/sources/sources.lisp b/src/sources/sources.lisp
index 9c39fd3..4342849 100644
--- a/src/sources/sources.lisp
+++ b/src/sources/sources.lisp
@@ -32,7 +32,7 @@
 			(slot-value source 'transforms))))
       (unless transforms
 	(setf (slot-value source 'transforms)
-	      (loop for c in (slot-value source 'columns) collect nil))))))
+              (make-list (length (slot-value source 'columns))))))))
 
 (defgeneric map-rows (source &key process-row-fn)
   (:documentation