diff --git a/contrib/micros-macrostep.lisp b/contrib/micros-macrostep.lisp
index d97900e..326e796 100644
--- a/contrib/micros-macrostep.lisp
+++ b/contrib/micros-macrostep.lisp
@@ -24,31 +24,34 @@
 (defslimefun macrostep-expand-1 (string compiler-macros? context)
   (with-buffer-syntax ()
     (let ((form (read-from-string string)))
-      (multiple-value-bind (expansion error-message)
-	  (expand-form-once form compiler-macros? context)
-	(if error-message
-            `(:error ,error-message)
-	    (multiple-value-bind (macros compiler-macros)
-		(collect-macro-forms-in-context expansion context)
-	      (let* ((all-macros (append macros compiler-macros))
-		     (pretty-expansion (pprint-to-string expansion))
-		     (positions (collect-form-positions expansion
-							pretty-expansion
-							all-macros))
-                     (subform-info
-                      (loop
-                         for form in all-macros
-                         for (start end) in positions
-                         when (and start end)
-                         collect (let ((op-name (to-string (first form)))
-                                       (op-type
-                                        (if (member form macros)
-                                            :macro
-                                            :compiler-macro)))
-                                   (list op-name
-                                         op-type
-                                         start)))))
-		`(:ok ,pretty-expansion ,subform-info))))))))
+      (handler-case 
+          (multiple-value-bind (expansion error-message)
+              (expand-form-once form compiler-macros? context)
+            (if error-message
+                `(:error ,error-message)
+                (multiple-value-bind (macros compiler-macros)
+                    (collect-macro-forms-in-context expansion context)
+                  (let* ((all-macros (append macros compiler-macros))
+                         (pretty-expansion (pprint-to-string expansion))
+                         (positions (collect-form-positions expansion
+                                                            pretty-expansion
+                                                            all-macros))
+                         (subform-info
+                           (loop
+                             for form in all-macros
+                             for (start end) in positions
+                             when (and start end)
+                             collect (let ((op-name (to-string (first form)))
+                                           (op-type
+                                             (if (member form macros)
+                                                 :macro
+                                                 :compiler-macro)))
+                                       (list op-name
+                                             op-type
+                                             start)))))
+                    `(:ok ,pretty-expansion ,subform-info)))))
+        (error (condition)
+          `(:error ,(princ-to-string condition)))))))
 
 (defun expand-form-once (form compiler-macros? context)
   (multiple-value-bind (expansion expanded?)