diff --git a/scheme/ikarus.boot.prebuilt b/scheme/ikarus.boot.prebuilt
index 6a91bc7..62d948d 100644
Binary files a/scheme/ikarus.boot.prebuilt and b/scheme/ikarus.boot.prebuilt differ
diff --git a/scheme/ikarus.load.ss b/scheme/ikarus.load.ss
index da1c431..6d1a895 100644
--- a/scheme/ikarus.load.ss
+++ b/scheme/ikarus.load.ss
@@ -18,9 +18,40 @@
   (export load load-r6rs-top-level)
   (import 
     (except (ikarus) load)
+    (only (ikarus.compiler) compile-core-expr)
+    (only (psyntax library-manager) 
+      serialize-all current-precompiled-library-loader)
     (only (psyntax expander) eval-top-level compile-r6rs-top-level)
     (only (ikarus reader) read-initial))
 
+
+  (define-struct serialized-library (contents))
+
+  (define (load-serialized-library filename sk)
+    ;;; TODO: check file last-modified date
+    (let ([ikfasl (string-append filename ".ikfasl")])
+      (and (file-exists? ikfasl)
+           (let ([x 
+                  (let ([p (open-file-input-port ikfasl)])
+                    (let ([x (fasl-read p)])
+                      (close-input-port p)
+                      x))])
+             (if (serialized-library? x)
+                 (apply sk (serialized-library-contents x))
+                 (begin
+                   (printf
+                      "WARNING: not using fasl file ~s because it was \
+                       compiled with a different version of ikarus.\n" 
+                      ikfasl)
+                   #f))))))
+
+  (define (do-serialize-library filename contents)
+    (let ([ikfasl (string-append filename ".ikfasl")])
+      (printf "Serializing ~s\n" ikfasl)
+      (let ([p (open-file-output-port ikfasl (file-options no-fail))])
+        (fasl-write (make-serialized-library contents) p)
+        (close-output-port p))))
+
   (define load-handler
     (lambda (x)
       (eval-top-level x)))
@@ -63,6 +94,14 @@
         (let ([thunk (compile-r6rs-top-level prog)])
           (case how
             [(run) (thunk)]
-            [(compile) (error 'load-r6rs "not yet")]
+            [(compile) 
+             (serialize-all 
+               (lambda (file-name contents)
+                 (do-serialize-library file-name contents))
+               (lambda (core-expr) 
+                 (compile-core-expr core-expr)))]
             [else (error 'load-r6rs-top-level "invali argument" how)])))))
+
+  (current-precompiled-library-loader load-serialized-library)
+  
   )
diff --git a/scheme/ikarus.main.ss b/scheme/ikarus.main.ss
index 3af5f7f..2abc5c3 100644
--- a/scheme/ikarus.main.ss
+++ b/scheme/ikarus.main.ss
@@ -90,14 +90,14 @@
                           (die 'ikarus "--r6rs-script requires a script name")]
                          [else
                           (values '() (car d) 'r6rs-script (cdr d))]))]
-                    [(string=? (car args) "--compile-r6rs-script")
+                    [(string=? (car args) "--compile-dependencies")
                      (let ([d (cdr args)])
                        (cond
                          [(null? d)
                           (die 'ikarus
                             "--compile-r6rs-script requires a script name")]
                          [else
-                          (values '() (car d) 'compile-r6rs-script (cdr d))]))]
+                          (values '() (car d) 'compile (cdr d))]))]
                     [else
                      (let-values ([(f* script script-type a*) (f (cdr args))])
                        (values (cons (car args) f*) script script-type a*))]))])
@@ -106,7 +106,7 @@
        (command-line-arguments (cons script args))
        (load-r6rs-top-level script 'run)
        (exit 0)]
-      [(eq? script-type 'compile-r6rs-script)
+      [(eq? script-type 'compile)
        (command-line-arguments (cons script args))
        (load-r6rs-top-level script 'compile)
        (exit 0)]
diff --git a/scheme/ikarus.posix.ss b/scheme/ikarus.posix.ss
index d5ae5e0..5674047 100644
--- a/scheme/ikarus.posix.ss
+++ b/scheme/ikarus.posix.ss
@@ -16,12 +16,12 @@
 
 (library (ikarus posix)
   (export posix-fork fork waitpid system file-exists? delete-file
-          getenv env environ)
+          getenv env environ file-ctime)
   (import 
     (rnrs bytevectors)
     (except (ikarus)
        posix-fork fork waitpid system file-exists? delete-file
-       getenv env environ))
+       getenv env environ file-ctime))
 
   (define posix-fork
     (lambda ()
@@ -102,6 +102,22 @@
                    [else "Unknown error while deleting file"]))
                (make-i/o-filename-error x)))]))))
 
+  (define (file-ctime x)
+    (define who 'file-ctime)
+    (unless (string? x) 
+      (die who "not a string" x))
+    (let ([p (cons #f #f)])
+      (let ([v (foreign-call "ikrt_file_ctime" (string->utf8 x) p)])
+        (case v
+          [(0) (+ (* (car p) #e1e9) (cdr p))]
+          [else 
+           (raise
+             (condition 
+               (make-who-condition who)
+               (make-message-condition "cannot stat a file")
+               (make-i/o-filename-error x)))]))))
+
+
   (define ($getenv-bv key)
     (foreign-call "ikrt_getenv" key))
   (define ($getenv-str key) 
diff --git a/scheme/last-revision b/scheme/last-revision
index 80b6d67..c4425ac 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1394
+1395
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index 508baf4..e483c93 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -1211,6 +1211,7 @@
     [vector-sort!                                i r sr]
     [file-exists?                                i r fi]
     [delete-file                                 i r fi]
+    [file-ctime                                  i]
     [define-record-type                          i r rs]
     [fields                                      i r rs]
     [immutable                                   i r rs]
diff --git a/scheme/psyntax.library-manager.ss b/scheme/psyntax.library-manager.ss
index 6037f89..424c8d1 100644
--- a/scheme/psyntax.library-manager.ss
+++ b/scheme/psyntax.library-manager.ss
@@ -23,7 +23,8 @@
     visit-library library-name library-version library-exists?
     find-library-by-name install-library library-spec invoke-library 
     extend-library-subst! extend-library-env! current-library-expander
-    current-library-collection library-path library-extensions)
+    current-library-collection library-path library-extensions
+    serialize-all current-precompiled-library-loader)
   (import (rnrs) (psyntax compat) (rnrs r5rs)
     (only (ikarus) printf))
 
@@ -157,9 +158,33 @@
             f
             (assertion-violation 'file-locator "not a procedure" f)))))
 
+  (define (serialize-all serialize compile)
+    (define (library-desc x) 
+      (list (library-id x) (library-name x)))
+    (for-each 
+      (lambda (x)
+        (when (library-source-file-name x) 
+          (serialize 
+            (library-source-file-name x)
+            (list (library-id x) 
+                  (library-name x)
+                  (library-version x) 
+                  (map library-desc (library-imp* x))
+                  (map library-desc (library-vis* x))
+                  (map library-desc (library-inv* x))
+                  (library-subst x)
+                  (library-env x)
+                  (compile (library-visit-code x))
+                  (compile (library-invoke-code x))
+                  (library-visible? x)))))
+      ((current-library-collection))))
 
+  (define current-precompiled-library-loader
+    (make-parameter (lambda (filename sk) #f)))
+        
   (define (try-load-from-file filename)
-    (load-precompiled-library filename
+    ((current-precompiled-library-loader)
+      filename
       (case-lambda
         [(id name ver imp* vis* inv* exp-subst exp-env
           visit-proc invoke-proc visible?)
@@ -172,7 +197,7 @@
              [(null? deps)
               (install-library id name ver imp* vis* inv* 
                 exp-subst exp-env visit-proc invoke-proc 
-                #f #f visible?)
+                #f #f visible? #f)
               #t]
              [else
               (let ([d (car deps)]) 
@@ -288,13 +313,7 @@
          (let ((lib (make-library id name ver imp-lib* vis-lib* inv-lib* 
                        exp-subst exp-env visit-proc invoke-proc 
                        visit-code invoke-code visible? source-file-name)))
-           (install-library-record lib)))]
-      #;[(id name ver imp* vis* inv* exp-subst exp-env 
-        visit-proc invoke-proc visit-code invoke-code 
-        visible?)
-       (install-library id name ver imp* vis* inv* exp-subst exp-env 
-          visit-proc invoke-proc visit-code invoke-code 
-          visible? #f)]))
+           (install-library-record lib)))]))
 
   (define extend-library-subst!
     (lambda (lib sym label)
diff --git a/src/ikarus-io.c b/src/ikarus-io.c
index c278a22..55ccc9e 100644
--- a/src/ikarus-io.c
+++ b/src/ikarus-io.c
@@ -186,3 +186,15 @@ ikrt_tcp_connect_nonblocking(ikptr host, ikptr srvc, ikpcb* pcb){
   return fdptr;
 }
 
+ikptr
+ikrt_file_ctime(ikptr filename, ikptr res){
+  struct stat s;
+  int err = stat((char*)(filename + off_bytevector_data), &s);
+  if(err) {
+    return fix(errno);
+  }
+  ref(res, off_car) = fix(s.st_ctimespec.tv_sec);
+  ref(res, off_cdr) = fix(s.st_ctimespec.tv_nsec);
+  return fix(0);
+}
+