diff --git a/scheme/ikarus.boot.prebuilt b/scheme/ikarus.boot.prebuilt
index 00d90fd..b1f06b5 100644
Binary files a/scheme/ikarus.boot.prebuilt and b/scheme/ikarus.boot.prebuilt differ
diff --git a/scheme/ikarus.io-primitives.ss b/scheme/ikarus.io-primitives.ss
index 6c13846..038f522 100644
--- a/scheme/ikarus.io-primitives.ss
+++ b/scheme/ikarus.io-primitives.ss
@@ -15,7 +15,7 @@
 
 
 (library (ikarus io-primitives)
-  (export read-char unread-char peek-char write-char write-byte
+  (export read-char peek-char write-char write-byte
           put-u8 put-char put-string put-bytevector 
           get-char get-u8 lookahead-u8
           get-string-n get-string-n! 
@@ -27,7 +27,7 @@
     (ikarus system $io)
     (ikarus system $fx)
     (ikarus system $ports)
-    (except (ikarus) read-char unread-char peek-char write-char write-byte 
+    (except (ikarus) read-char peek-char write-char write-byte 
             put-u8 put-char put-string put-bytevector
             get-char get-u8 lookahead-u8
             get-string-n get-string-n! 
@@ -134,18 +134,6 @@
            ($read-char p)
            (error 'read-char "not an input-port" p))]))
   ;;;
-  (define unread-char
-    (case-lambda
-      [(c) (if (char? c)
-               ($unread-char c (current-input-port))
-               (error 'unread-char "not a character" c))]
-      [(c p)
-       (if (input-port? p)
-           (if (char? c)
-               ($unread-char c p)
-               (error 'unread-char "not a character" c))
-           (error 'unread-char "not an input-port" p))]))
-  ;;;
   (define peek-char
     (case-lambda
       [() ($peek-char (current-input-port))]
diff --git a/scheme/ikarus.io-primitives.unsafe.ss b/scheme/ikarus.io-primitives.unsafe.ss
index 248a0a4..ee142af 100644
--- a/scheme/ikarus.io-primitives.unsafe.ss
+++ b/scheme/ikarus.io-primitives.unsafe.ss
@@ -16,7 +16,7 @@
 
 (library (ikarus io-primitives unsafe)
   (export $write-char $write-byte $read-char $get-u8 $lookahead-u8
-          $unread-char $peek-char
+          $peek-char
           $reset-input-port! $flush-output-port 
           $close-input-port $close-output-port)
   (import
@@ -103,18 +103,6 @@
                   [else (($port-handler p) 'peek-char p)]))
             (($port-handler p) 'peek-char p)))))
 
-  (define $unread-char
-    (lambda (c p)
-      (let ([idx ($fxsub1 ($port-index p))]
-            [b ($char->fixnum c)])
-        (if (and ($fx<= b 127)
-                 ($fx>= idx 0)
-                 ($fx< idx ($port-size p)))
-            (begin
-              ($set-port-index! p idx)
-              ($bytevector-set! ($port-buffer p) idx b))
-            (($port-handler p) 'unread-char c p)))))
-
   (define $reset-input-port!
     (lambda (p)
       ($set-port-size! p 0)))
diff --git a/scheme/ikarus.io.input-files.ss b/scheme/ikarus.io.input-files.ss
index 0b4bd55..1b31abf 100644
--- a/scheme/ikarus.io.input-files.ss
+++ b/scheme/ikarus.io.input-files.ss
@@ -91,9 +91,6 @@
   (define peek-multibyte-char 
     (lambda (p)
       (error 'peek-multibyte-char "not implemented")))
-  (define unread-multibyte-char 
-    (lambda (c p)
-      (error 'unread-multibyte-char "not implemented")))
 
   (define make-input-file-handler
     (lambda (fd port-name)
@@ -188,22 +185,6 @@
                            [else
                             ($bytevector-u8-ref ($port-buffer p) 0)]))
                        (error 'lookahead-u8 "port is closed" p))))]
-            [(unread-char c p)
-             (unless (input-port? p)
-               (error 'unread-char "not an input port" p))
-             (let ([idx ($fxsub1 ($port-index p))]
-                   [b (if (char? c) 
-                          ($char->fixnum c)
-                          (error 'unread-char "not a char" c))])
-               (if (and ($fx>= idx 0)
-                        ($fx< idx ($port-size p)))
-                   (cond
-                     [($fx< b 128)
-                      ($set-port-index! p idx)]
-                     [else (unread-multibyte-char c p)])
-                   (if open?
-                       (error 'unread-char "port is closed" p)
-                       (error 'unread-char "too many unread-chars"))))]
             [(port-name p) port-name]
             [(close-port p)
              (unless (input-port? p)
diff --git a/scheme/ikarus.io.input-strings.ss b/scheme/ikarus.io.input-strings.ss
index 83e2b53..b6a3a66 100644
--- a/scheme/ikarus.io.input-strings.ss
+++ b/scheme/ikarus.io.input-strings.ss
@@ -68,14 +68,6 @@
                  (if open?
                      (eof-object)
                      (error 'peek-char "port is closed" p)))]
-            [(unread-char c p)
-             (let ([i ($fxsub1 idx)])
-               (if (and ($fx>= i 0)
-                        ($fx< i n))
-                   (set! idx i)
-                   (if open?
-                       (error 'unread-char "port is closed" p)
-                       (error 'unread-char "too many unread-chars"))))]
             [(port-name p) '*string-port*]
             [(close-port p)
              (when open?
diff --git a/scheme/ikarus.reader.ss b/scheme/ikarus.reader.ss
index a2ec3ce..fddc998 100644
--- a/scheme/ikarus.reader.ss
+++ b/scheme/ikarus.reader.ss
@@ -64,17 +64,17 @@
       (memq c '(#\+ #\- #\. #\@))))
   (define tokenize-identifier
     (lambda (ls p)
-      (let ([c (read-char p)])
+      (let ([c (peek-char p)])
         (cond
          [(eof-object? c) ls]
          [(subsequent? c)
-          (tokenize-identifier (cons c ls) p)]
+          (tokenize-identifier (cons (read-char p) ls) p)]
          [(delimiter? c)
-          (unread-char c p)
           ls]
-         [(char=? c #\\) (tokenize-backslash ls p)]
+         [(char=? c #\\)
+          (read-char p)
+          (tokenize-backslash ls p)]
          [else
-          (unread-char c p)
           (error 'tokenize "invalid identifier syntax" 
                  (list->string (reverse (cons c ls))))]))))
   (define (tokenize-string ls p)
@@ -193,11 +193,12 @@
           [(delimiter? c)  'dot]
           [($char= c #\.)  ; this is second dot
            (read-char p)
-           (let ([c (read-char p)])
+           (let ([c (peek-char p)])
              (cond
                [(eof-object? c) 
                 (error 'tokenize "invalid syntax .. near end of file")]
                [($char= c #\.) ; this is the third
+                (read-char p)
                 (let ([c (peek-char p)])
                   (cond
                     [(eof-object? c) '(datum . ...)]
@@ -206,7 +207,6 @@
                      (error 'tokenize "invalid syntax"
                             (string-append "..." (string c)))]))]
                [else
-                (unread-char c p)
                 (error 'tokenize "invalid syntax"
                        (string-append ".." (string c)))]))]
           [else 
@@ -296,15 +296,15 @@
                 (lambda (v) 
                   (read-char p)
                   (let f ([v v])
-                    (let ([c (read-char p)])
+                    (let ([c (peek-char p)])
                       (cond
                         [(eof-object? c)
                          (cons 'datum (integer->char v))]
                         [(delimiter? c)
-                         (unread-char c p)
                          (cons 'datum (integer->char v))]
                         [(hex c) =>
                          (lambda (v0)
+                           (read-char p)
                            (f (+ (* v 16) v0)))]
                         [else
                          (error 'tokenize "invalid character sequence")]))))]
@@ -539,7 +539,6 @@
          (error 'read "FIXME: fasl read disabled")
          '(cons 'datum ($fasl-read p))]
         [else 
-         (unread-char c p)
          (error 'tokenize 
             (format "invalid syntax #~a" c))])))
   (define (tokenize-exactness-mark p ls exact?)
@@ -636,43 +635,47 @@
              (tokenize-denom p (cons c ls) exact? radix num d))]
           [else (num-error "invalid sequence" (cons c ls))])))
     (define (tokenize-denom p ls exact? radix num ac)
-      (let ([c (read-char p)])
+      (let ([c (peek-char p)])
         (cond
           [(eof-object? c) 
+           (read-char p)
            (if (= ac 0) 
                (num-error "zero denominator" ls)
                (convert/exact exact? (/ num ac)))]
           [(radix-digit c radix) =>
            (lambda (d) 
+             (read-char p)
              (tokenize-denom p (cons c ls) exact? radix num 
                 (+ (* radix ac) d)))]
           [(delimiter? c) 
-           (unread-char c p)
-           (if (= ac 0) 
+           (if (= ac 0)
                (num-error "zero denominator" ls)
                (convert/exact exact? (/ num ac)))]
           [else (num-error "invalid sequence" (cons c ls))])))
-    (let ([c (read-char p)])
+    (let ([c (peek-char p)])
       (cond
         [(eof-object? c) (convert/exact exact? ac)]
         [(radix-digit c radix) =>
          (lambda (d)
+           (read-char p)
            (tokenize-integer p (cons c ls) exact? radix 
              (+ (* ac radix) d)))]
         [(char=? c #\.)
          (unless (= radix 10)
            (num-error "invalid decimal" (cons c ls)))
+         (read-char p)
          (tokenize-decimal p (cons c ls) exact? ac 0)]
         [(char=? c #\/)
+         (read-char p)
          (tokenize-denom-start p (cons #\/ ls) exact? radix ac)]
         [(memv c '(#\e #\E)) ; exponent
+         (read-char p)
          (unless (= radix 10)
            (num-error "invalid decimal" (cons c ls)))
          (let ([ex (tokenize-exponent-start p (cons c ls))])
            (convert/exact (or exact? 'i)
              (* ac (expt radix ex))))]
         [(delimiter? c)
-         (unread-char c p)
          (convert/exact exact? ac)]
         [else (num-error "invalid sequence" (cons c ls))])))
   (define (tokenize-exponent-start p ls)
@@ -685,16 +688,15 @@
              (tokenize-exponent p (cons c ls) d))]
           [else (num-error "invalid sequence" (cons c ls))])))
     (define (tokenize-exponent p ls ac)
-      (let ([c (read-char p)])
+      (let ([c (peek-char p)])
         (cond
           [(eof-object? c) ac]
           [(radix-digit c 10) =>
            (lambda (d) 
+             (read-char p)
              (tokenize-exponent p (cons c ls) 
                (+ (* ac 10) d)))]
-          [(delimiter? c)
-           (unread-char c p)
-           ac]
+          [(delimiter? c) ac]
           [else (num-error "invalid sequence" (cons c ls))])))
     (let ([c (read-char p)])
       (cond
@@ -708,21 +710,22 @@
          (tokenize-exponent-no-digits p (cons c ls))]
         [else (num-error "invalid sequence" (cons c ls))])))
   (define (tokenize-decimal p ls exact? ac exp)
-    (let ([c (read-char p)])
+    (let ([c (peek-char p)])
       (cond
         [(eof-object? c) 
          (let ([ac (* ac (expt 10 exp))])
            (convert/exact (or exact? 'i) ac))]
         [(radix-digit c 10) =>
          (lambda (d) 
+           (read-char p)
            (tokenize-decimal p (cons c ls) exact? 
              (+ (* ac 10) d) (- exp 1)))]
         [(memv c '(#\e #\E)) 
+         (read-char p)
          (let ([ex (tokenize-exponent-start p (cons c ls))])
            (let ([ac (* ac (expt 10 (+ exp ex)))])
              (convert/exact (or exact? 'i) ac)))]
         [(delimiter? c) 
-         (unread-char c p)
          (let ([ac (* ac (expt 10 exp))])
            (convert/exact (or exact? 'i) ac))]
         [else (num-error "invalid sequence" (cons c ls))])))
@@ -778,19 +781,16 @@
         [else
          (let ([c (read-char p)])
            (cond
-             [else
-              (cond
-                [(eof-object? c) 
-                 (error 'tokenize
-                   (format "invalid eof inside ~a" who))]
-                [(or (and (not ci?) (char=? c (string-ref str i)))
-                     (and ci? (char=? (char-downcase c) (string-ref str i))))
-                 (f (add1 i) (cons c ls))]
-                [else 
-                 (unread-char c p)
-                 (error 'tokenize 
-                   (format "invalid ~a: ~s" who
-                     (list->string (reverse (cons c ls)))))])]))])))
+             [(eof-object? c) 
+              (error 'tokenize
+                (format "invalid eof inside ~a" who))]
+             [(or (and (not ci?) (char=? c (string-ref str i)))
+                  (and ci? (char=? (char-downcase c) (string-ref str i))))
+              (f (add1 i) (cons c ls))]
+             [else 
+              (error 'tokenize 
+                (format "invalid ~a: ~s" who
+                  (list->string (reverse (cons c ls)))))]))])))
   (define (tokenize-integer/nan/inf-no-digits p ls)
     (let ([c (read-char p)])
       (cond
@@ -832,7 +832,6 @@
         [(digit? c)
          (tokenize-hashnum p (fx+ (fx* n 10) (char->num c)))]
         [else
-         (unread-char c p)
          (error 'tokenize "invalid char while inside a #n mark/ref" c)])))
   (define tokenize-bar
     (lambda (p ac)
@@ -876,11 +875,9 @@
                        (error 'tokenize "invalid sequence"
                          (list->string (cons c (reverse ac))))]))))]
              [else
-              (unread-char c p) 
               (error 'tokenize 
                  (format "invalid sequence \\x~a" c))]))]
         [else 
-         (unread-char c p) 
          (error 'tokenize
            (format "invalid sequence \\~a" c))])))
   (define tokenize/c
@@ -950,7 +947,6 @@
               (list->string
                 (reverse (tokenize-backslash '() p)))))]
         [else
-         (unread-char c p) 
          (error 'tokenize "invalid syntax" c)])))
 
   (define tokenize
diff --git a/scheme/last-revision b/scheme/last-revision
index 3fe2180..03183b0 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1186
+1187
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index 51b29d2..fe7c196 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -354,7 +354,7 @@
     [reset-input-port!                           i]
     [write-byte                                  i]
     [read-token                                  i]
-    [unread-char                                 i]
+    ;[unread-char                                 i]
     [printf                                      i]
     [fprintf                                     i]
     [format                                      i]
@@ -540,7 +540,6 @@
     [$write-byte                                 $io]
     [$read-char                                  $io]
     [$peek-char                                  $io]
-    [$unread-char                                $io]
     [$arg-list                                   $arg-list]
     [$collect-key                                $arg-list]
     [$$apply                                     $stack]