diff --git a/eval.c b/eval.c
index 4fd78faa..82360178 100644
--- a/eval.c
+++ b/eval.c
@@ -1891,6 +1891,19 @@ sexp sexp_read_utf8_char (sexp ctx, sexp port, int i) {
   return sexp_make_character(i);
 }
 
+void sexp_push_utf8_char (sexp ctx, int i, sexp port) {
+  unsigned char ch[6];
+  int len = sexp_utf8_char_byte_count(i);
+  sexp_utf8_encode_char(ch, len, i);
+  if (sexp_port_stream(port))  {
+    while (len>0)
+      ungetc(ch[--len], sexp_port_stream(port));
+  } else {
+    while (len>0)
+      sexp_port_buf(port)[--sexp_port_offset(port)] = ch[--len];
+  }
+}
+
 #if SEXP_USE_MUTABLE_STRINGS
 
 void sexp_string_utf8_set (sexp ctx, sexp str, sexp index, sexp ch) {
diff --git a/include/chibi/eval.h b/include/chibi/eval.h
index 3f6ca257..99e673ae 100644
--- a/include/chibi/eval.h
+++ b/include/chibi/eval.h
@@ -137,6 +137,7 @@ SEXP_API sexp sexp_make_promise (sexp ctx, sexp self, sexp_sint_t n, sexp done,
 #endif
 #if SEXP_USE_UTF8_STRINGS
 SEXP_API sexp sexp_read_utf8_char (sexp ctx, sexp port, int i);
+SEXP_API void sexp_push_utf8_char (sexp ctx, int i, sexp port);
 SEXP_API void sexp_string_utf8_set (sexp ctx, sexp str, sexp index, sexp ch);
 SEXP_API sexp sexp_string_utf8_index_ref (sexp ctx, sexp self, sexp_sint_t n, sexp str, sexp i);
 SEXP_API sexp sexp_string_utf8_index_set (sexp ctx, sexp self, sexp_sint_t n, sexp str, sexp i, sexp ch);
diff --git a/lib/chibi/io-test.sld b/lib/chibi/io-test.sld
index 642569f8..1374e651 100644
--- a/lib/chibi/io-test.sld
+++ b/lib/chibi/io-test.sld
@@ -131,7 +131,7 @@
                    (lambda (bv start end)
                      (do ((j start (+ j 1)))
                          ((= j end))
-                       (bytevector-u8-set! bv j (modulo (+ j i) 256)))
+                       (bytevector-u8-set! bv j (modulo (- (+ j i) start) 256)))
                      (if (> end 0)
                          (set! i (bytevector-u8-ref bv (- end 1))))
                      (- end start))))))
diff --git a/lib/chibi/io/io.scm b/lib/chibi/io/io.scm
index 6d9cb4ea..0f6025d4 100644
--- a/lib/chibi/io/io.scm
+++ b/lib/chibi/io/io.scm
@@ -378,7 +378,7 @@
                (set! buf "")
                (set! len 0)
                (set! offset 0)
-               (+ i start))
+               i)
               (else
                (set! len (string-size buf))
                (cond
diff --git a/sexp.c b/sexp.c
index 82d10c5e..1c485fd9 100644
--- a/sexp.c
+++ b/sexp.c
@@ -1338,6 +1338,9 @@ sexp sexp_make_cpointer (sexp ctx, sexp_uint_t type_id, void *value,
 
 /************************ reading and writing *************************/
 
+/* start 4 bytes in so we can always unread a utf8 char in peek-char */
+#define BUF_START 4
+
 int sexp_buffered_read_char (sexp ctx, sexp p) {
   sexp_gc_var2(tmp, origbytes);
   int res = 0;
@@ -1346,29 +1349,29 @@ int sexp_buffered_read_char (sexp ctx, sexp p) {
   } else if (!sexp_port_openp(p)) {
     return EOF;
   } else if (sexp_port_stream(p)) {
-    res = fread(sexp_port_buf(p), 1, SEXP_PORT_BUFFER_SIZE, sexp_port_stream(p));
+    res = fread(sexp_port_buf(p) + BUF_START, 1, SEXP_PORT_BUFFER_SIZE - BUF_START, sexp_port_stream(p));
     if (res >= 0) {
-      sexp_port_offset(p) = 0;
+      sexp_port_offset(p) = BUF_START;
       sexp_port_size(p) = res;
       res = ((sexp_port_offset(p) < sexp_port_size(p))
              ? ((unsigned char*)sexp_port_buf(p))[sexp_port_offset(p)++] : EOF);
     }
   } else if (sexp_filenop(sexp_port_fd(p))) {
-    res = read(sexp_port_fileno(p), sexp_port_buf(p), SEXP_PORT_BUFFER_SIZE);
+    res = read(sexp_port_fileno(p), sexp_port_buf(p) + BUF_START, SEXP_PORT_BUFFER_SIZE - BUF_START);
     if (res >= 0) {
-      sexp_port_offset(p) = 0;
+      sexp_port_offset(p) = BUF_START;
       sexp_port_size(p) = res;
       res = ((sexp_port_offset(p) < sexp_port_size(p))
              ? ((unsigned char*)sexp_port_buf(p))[sexp_port_offset(p)++] : EOF);
     }
   } else if (sexp_port_customp(p)) {
     sexp_gc_preserve2(ctx, tmp, origbytes);
-    tmp = sexp_list2(ctx, SEXP_ZERO, sexp_make_fixnum(SEXP_PORT_BUFFER_SIZE));
+    tmp = sexp_list2(ctx, sexp_make_fixnum(BUF_START), sexp_make_fixnum(SEXP_PORT_BUFFER_SIZE));
     origbytes = sexp_port_binaryp(p) && !SEXP_USE_PACKED_STRINGS ? sexp_string_bytes(sexp_port_buffer(p)) : sexp_port_buffer(p);
     tmp = sexp_cons(ctx, origbytes, tmp);
     tmp = sexp_apply(ctx, sexp_port_reader(p), tmp);
-    if (sexp_fixnump(tmp) && sexp_unbox_fixnum(tmp) > 0) {
-      sexp_port_offset(p) = 0;
+    if (sexp_fixnump(tmp) && sexp_unbox_fixnum(tmp) > BUF_START) {
+      sexp_port_offset(p) = BUF_START;
       sexp_port_size(p) = sexp_unbox_fixnum(tmp);
       if (!sexp_port_binaryp(p) && !SEXP_USE_PACKED_STRINGS
           && origbytes != sexp_string_bytes(sexp_port_buffer(p))) {
diff --git a/tests/r7rs-tests.scm b/tests/r7rs-tests.scm
index e08412ff..20f8a512 100644
--- a/tests/r7rs-tests.scm
+++ b/tests/r7rs-tests.scm
@@ -1905,9 +1905,11 @@
 (test "abc" (read-string 3 (open-input-string "abc\ndef\n")))
 
 (let ((in (open-input-string (string #\x10F700 #\x10F701 #\x10F702))))
-  (let* ((c1 (read-char in))
+  (let* ((c0 (peek-char in))
+         (c1 (read-char in))
          (c2 (read-char in))
          (c3 (read-char in)))
+    (test #\x10F700 c0)
     (test #\x10F700 c1)
     (test #\x10F701 c2)
     (test #\x10F702 c3)))
diff --git a/vm.c b/vm.c
index 960d7809..132f2236 100644
--- a/vm.c
+++ b/vm.c
@@ -2081,7 +2081,7 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
 #endif
     if (i == EOF) {
       if (!sexp_port_openp(_ARG1))
-        sexp_raise("peek-char: port is closed", _ARG1);
+        sexp_raise("read-char: port is closed", _ARG1);
       else
 #if SEXP_USE_GREEN_THREADS
       if ((sexp_port_stream(_ARG1) ? ferror(sexp_port_stream(_ARG1)) : 1)
@@ -2113,7 +2113,7 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
     i = sexp_read_char(ctx, _ARG1);
     if (i == EOF) {
       if (!sexp_port_openp(_ARG1))
-        sexp_raise("read-char: port is closed", _ARG1);
+        sexp_raise("peek-char: port is closed", _ARG1);
       else
 #if SEXP_USE_GREEN_THREADS
       if ((sexp_port_stream(_ARG1) ? ferror(sexp_port_stream(_ARG1)) : 1)
@@ -2128,6 +2128,12 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
       } else
 #endif
         _ARG1 = SEXP_EOF;
+#if SEXP_USE_UTF8_STRINGS
+    } else if (i >= 0x80) {
+      tmp1 = sexp_read_utf8_char(ctx, _ARG1, i);
+      sexp_push_utf8_char(ctx, sexp_unbox_character(tmp1), _ARG1);
+      _ARG1 = tmp1;
+#endif
     } else {
       sexp_push_char(ctx, i, _ARG1);
       _ARG1 = sexp_make_character(i);