diff --git a/modules.scm b/modules.scm
index b0cdce5..c310553 100644
--- a/modules.scm
+++ b/modules.scm
@@ -44,6 +44,12 @@
 	chicken.platform
 	chicken.syntax)
 
+(define (make-hash-table #!optional _test _hash (size 301))
+  (make-vector size '()))
+(define (hash-table-exists? t k) (and (hash-table-ref t k) #t))
+
+;; (import (only (srfi 69) symbol-hash hash-table-exists? hash-table-set! make-hash-table))
+
 (include "common-declarations.scm")
 (include "mini-srfi-1.scm")
 
@@ -294,15 +300,31 @@
 			  (warn "indirect export of unknown binding" (car iexports))
 			  (loop2 (cdr iexports)))))))))))
 
-(define (merge-se . ses)		; later occurrences take precedence
-  (let bwd ((ses (remove null? ses)))
-    (cond ((null? ses) '())
-	  ((null? (cdr ses)) (car ses))	; Do not re-cons the final list
-	  (else (let fwd ((se (car ses))
-			  (rest (bwd (cdr ses))))
-		  (cond ((null? se) rest)
-			((assq (caar se) rest) (fwd (cdr se) rest))
-			(else (cons (car se) (fwd (cdr se) rest)))))))))
+(define (merge-se . ses*) ; later occurrences take precedence to earlier ones
+  (let ([seen (make-hash-table)]
+	[rses (reverse ses*)])
+    (let loop ([ses (cdr rses)]
+	       [last-se #f]
+	       [se2 (car rses)])
+      (cond
+       [(null? ses) se2]
+       [(or (eq? last-se (car ses))
+	    (null? (car ses)))
+       	(loop (cdr ses) last-se se2)]
+       [(not last-se)
+	(unless (null? ses)
+	  (for-each (lambda (e) (hash-table-set! seen (car e) #t)) se2))
+	(loop ses se2 se2)]
+       [else
+	(let lp ([se (car ses)]
+		 [se2 se2])
+	  (cond
+	   [(null? se) (loop (cdr ses) (car ses) se2)]
+	   [(hash-table-exists? seen (caar se))
+	    (lp (cdr se) se2)]
+	   [else
+	    (hash-table-set! seen (caar se) #t)
+	    (lp (cdr se) (cons (car se) se2))]))]))))
 
 (define (##sys#compiled-module-registration mod)
   (let ((dlist (module-defined-list mod))