diff --git a/wip-duuqnd/user-side-compiler/middle/jigs.lisp b/wip-duuqnd/user-side-compiler/middle/jigs.lisp
index e3aebed..56b2927 100644
--- a/wip-duuqnd/user-side-compiler/middle/jigs.lisp
+++ b/wip-duuqnd/user-side-compiler/middle/jigs.lisp
@@ -40,6 +40,19 @@
 
 ;;; Compilation setup
 
+(defun make-iblock-names-unique (start-iblock)
+  (let ((encountered '()))
+    (do-iblocks (iblock start-iblock)
+      (let ((existing (assoc (name iblock) encountered :test #'equalp)))
+        (if existing
+            (progn
+              (setf (name iblock)
+                    (format nil "~A_~A" (name iblock) (incf (cdr existing)))))
+            (progn
+              (push (cons (copy-seq (name iblock)) 1) encountered)
+              (setf (name iblock)
+                    (format nil "~A_1" (name iblock)))))))))
+
 (defun fix-iblock-flow (start-iblock)
   (let ((reached '())
         (last nil)
@@ -77,7 +90,9 @@
            ,@body)
        (when ,add-return-p
          (build-insert-end (make-instance 'ir-return) ,builder))
-       (fix-iblock-flow ,iblock))))
+       (fix-iblock-flow ,iblock)
+       (unless (null (next ,iblock))
+         (make-iblock-names-unique (next ,iblock))))))
 
 ;;; Some quick example code