diff --git a/ledger-exec.el b/ledger-exec.el
index 152d6b81..ccb3a3b2 100644
--- a/ledger-exec.el
+++ b/ledger-exec.el
@@ -89,7 +89,8 @@ otherwise the error output is displayed and an error is raised."
                    (apply #'call-process-region
                           (append (list (point-min) (point-max)
                                         ledger-binary-path nil (list outbuf errfile) nil "-f" "-")
-                                  (list "--date-format" ledger-default-date-format)
+                                  (when ledger-default-date-format
+                                    (list "--date-format" ledger-default-date-format))
                                   args)))))
             (if (ledger-exec-success-p exit-code outbuf)
                 outbuf
diff --git a/ledger-init.el b/ledger-init.el
index acf1d615..5f7d1682 100644
--- a/ledger-init.el
+++ b/ledger-init.el
@@ -49,7 +49,7 @@ This variable is automatically populated by
   "The date format that ledger uses throughout.
 Set this to the value of `ledger-iso-date-format' if you prefer
 ISO 8601 dates."
-  :type 'string
+  :type '(choice string (const nil))
   :package-version '(ledger-mode . "4.0.0")
   :group 'ledger)
 
@@ -59,11 +59,13 @@ Returns the current date if DATE is nil or not supplied.
 
 If FORMAT is provided, use that as the date format.  Otherwise,
 use the --input-date-format specified in `ledger-init-file-name',
-or if none, use `ledger-default-date-format'."
+or if none, use `ledger-default-date-format'. If none of
+the previous values exist, use ledger-iso-date-format."
   (format-time-string
    (or format
        (cdr (assoc "input-date-format" ledger-environment-alist))
-       ledger-default-date-format)
+       ledger-default-date-format
+       ledger-iso-date-format)
    date))
 
 
diff --git a/ledger-reconcile.el b/ledger-reconcile.el
index db5cf126..66d36c9c 100644
--- a/ledger-reconcile.el
+++ b/ledger-reconcile.el
@@ -89,7 +89,7 @@ reconcile-finish will mark all pending posting cleared."
 (defcustom ledger-reconcile-default-date-format ledger-default-date-format
   "Date format for the reconcile buffer.
 Default is `ledger-default-date-format'."
-  :type 'string
+  :type '(custom string (const nil))
   :group 'ledger-reconcile)
 
 (defcustom ledger-reconcile-target-prompt-string "Target amount for reconciliation "