diff --git a/src/lsp/loop.lsp b/src/lsp/loop.lsp
index c696c3e8..1bdee923 100644
--- a/src/lsp/loop.lsp
+++ b/src/lsp/loop.lsp
@@ -659,8 +659,19 @@ collected result will be returned as the value of the LOOP."
   (cond
     ((null tree) (car (push (gensym) *ignores*)))
     ((atom tree) tree)
-    (t (cons (subst-gensyms-for-nil (car tree))
-             (subst-gensyms-for-nil (cdr tree))))))
+    ((atom (cdr tree))
+     (cons (subst-gensyms-for-nil (car tree))
+           (subst-gensyms-for-nil (cdr tree))))
+    (t
+     (do* ((acc (cons '&optional nil))
+           (acc-last acc)
+           (elt tree (cdr elt)))
+          ((atom elt)
+           (setf (cdr acc-last) elt)
+           acc)
+       (setf (cdr acc-last)
+             (cons (subst-gensyms-for-nil (car elt)) nil))
+       (setf acc-last (cdr acc-last))))))
  
 (defun loop-build-destructuring-bindings (crocks forms)
   (if crocks
diff --git a/src/tests/normal-tests/ansi.lsp b/src/tests/normal-tests/ansi.lsp
index 2df7ed8c..b489199f 100644
--- a/src/tests/normal-tests/ansi.lsp
+++ b/src/tests/normal-tests/ansi.lsp
@@ -45,41 +45,67 @@
     (is-true  (typep '* '(nest (3) 3)))
     (is-true  (typep  3 '(nest (2) 3)))))
 
+
+;;; 6. Iteration
+
+;;; Regression test for #605.
+(test ansi.6.1.1.7-destructuring
+  (finishes
+   (loop with (a b) = '(1)
+         do (return (list a b))))
+  (finishes
+   (loop with (a b . rest) = '(1)
+         do (return (list a b rest))))
+  (is-equal '(1 nil 2 nil)
+            (loop with (a b) = '(1)
+                  for  (c d) = '(2)
+                  do (return (list a b c d))))
+  (is-equal '(1 nil 2 nil nil)
+            (loop with (a b . rest) = '(1)
+                  for  (c d) = '(2)
+                  do (return (list a b c d rest))))
+  (is-equal '(1 2 nil)
+            (loop for (a (b) ((c))) ='(1 (2))
+                  do (return (list a b c))))
+  (signals error
+           (loop for (a (b)) ='(1 2)
+                 do (return (list a b)))))
+
 
 ;;; 8. Structures
 (ext:with-clean-symbols
     (my-struct make-my-struct my-struct-2 make-my-struct-2 my-struct-compatible-type)
- (test ansi.8.redefine-compatible
-       (let (foo-1 foo-2 foo-3 foo-4)
-         (defstruct (my-struct (:constructor make-my-struct)) slot-1 slot-2)
-         (setq foo-1 (make-my-struct :slot-1 3 :slot-2 4))
-         (finishes (defstruct (my-struct (:constructor make-my-struct))
-                     (slot-1 nil)
-                     (slot-2 t)))
-         (setq foo-2 (make-my-struct :slot-1 3 :slot-2 4))
-         (finishes (defstruct (my-struct (:constructor make-my-struct))
-                     (slot-1 3)
-                     (slot-2 4)))
-         (setq foo-3 (make-my-struct))
-         (finishes (defstruct (my-struct (:constructor make-my-struct))
-                     (slot-1 8 :type t :read-only nil)
-                     (slot-2 8 :type t :read-only nil)))
-         (setq foo-4 (make-my-struct :slot-1 3 :slot-2 4))
-         (is (equalp foo-1 foo-2))
-         (is (equalp foo-2 foo-3))
-         (is (equalp foo-3 foo-4)))
-       (deftype my-struct-compatible-type () `(integer 0 10))
-       (defstruct (my-struct-2 (:constructor make-my-struct-2))
-         (slot-1 nil :type my-struct-compatible-type :read-only t))
-       (finishes
-        (defstruct my-struct-2
-          (slot-1 nil :type (integer 0 10) :read-only t)))
-       (finishes
-        (defstruct my-struct-2
-          (slot-1 4 :type (integer 0 10) :read-only t)))
-       (finishes
-        (defstruct my-struct-2
-          (slot-1 4 :type (integer 0 10) :read-only nil)))))
+  (test ansi.8.redefine-compatible
+        (let (foo-1 foo-2 foo-3 foo-4)
+          (defstruct (my-struct (:constructor make-my-struct)) slot-1 slot-2)
+          (setq foo-1 (make-my-struct :slot-1 3 :slot-2 4))
+          (finishes (defstruct (my-struct (:constructor make-my-struct))
+                      (slot-1 nil)
+                      (slot-2 t)))
+          (setq foo-2 (make-my-struct :slot-1 3 :slot-2 4))
+          (finishes (defstruct (my-struct (:constructor make-my-struct))
+                      (slot-1 3)
+                      (slot-2 4)))
+          (setq foo-3 (make-my-struct))
+          (finishes (defstruct (my-struct (:constructor make-my-struct))
+                      (slot-1 8 :type t :read-only nil)
+                      (slot-2 8 :type t :read-only nil)))
+          (setq foo-4 (make-my-struct :slot-1 3 :slot-2 4))
+          (is (equalp foo-1 foo-2))
+          (is (equalp foo-2 foo-3))
+          (is (equalp foo-3 foo-4)))
+        (deftype my-struct-compatible-type () `(integer 0 10))
+        (defstruct (my-struct-2 (:constructor make-my-struct-2))
+          (slot-1 nil :type my-struct-compatible-type :read-only t))
+        (finishes
+         (defstruct my-struct-2
+           (slot-1 nil :type (integer 0 10) :read-only t)))
+        (finishes
+         (defstruct my-struct-2
+           (slot-1 4 :type (integer 0 10) :read-only t)))
+        (finishes
+         (defstruct my-struct-2
+           (slot-1 4 :type (integer 0 10) :read-only nil)))))
 
 (ext:with-clean-symbols (my-struct make-my-struct)
   (test ansi.8.redefine-incompatible