diff --git a/io_buffer.c b/io_buffer.c
index 1ff3935094f2a3..2fc7ac8a80f698 100644
--- a/io_buffer.c
+++ b/io_buffer.c
@@ -2430,7 +2430,7 @@ rb_io_buffer_read(VALUE self, VALUE io, size_t length, size_t offset)
 {
     VALUE scheduler = rb_fiber_scheduler_current();
     if (scheduler != Qnil) {
-        VALUE result = rb_fiber_scheduler_io_read(scheduler, io, self, SIZET2NUM(length), SIZET2NUM(offset));
+        VALUE result = rb_fiber_scheduler_io_read(scheduler, io, self, length, offset);
 
         if (!UNDEF_P(result)) {
             return result;
@@ -2544,7 +2544,7 @@ rb_io_buffer_pread(VALUE self, VALUE io, rb_off_t from, size_t length, size_t of
 {
     VALUE scheduler = rb_fiber_scheduler_current();
     if (scheduler != Qnil) {
-        VALUE result = rb_fiber_scheduler_io_pread(scheduler, io, OFFT2NUM(from), self, SIZET2NUM(length), SIZET2NUM(offset));
+        VALUE result = rb_fiber_scheduler_io_pread(scheduler, io, from, self, length, offset);
 
         if (!UNDEF_P(result)) {
             return result;
@@ -2649,7 +2649,7 @@ rb_io_buffer_write(VALUE self, VALUE io, size_t length, size_t offset)
 {
     VALUE scheduler = rb_fiber_scheduler_current();
     if (scheduler != Qnil) {
-        VALUE result = rb_fiber_scheduler_io_write(scheduler, io, self, SIZET2NUM(length), SIZET2NUM(offset));
+        VALUE result = rb_fiber_scheduler_io_write(scheduler, io, self, length, offset);
 
         if (!UNDEF_P(result)) {
             return result;
@@ -2753,7 +2753,7 @@ rb_io_buffer_pwrite(VALUE self, VALUE io, rb_off_t from, size_t length, size_t o
 {
     VALUE scheduler = rb_fiber_scheduler_current();
     if (scheduler != Qnil) {
-        VALUE result = rb_fiber_scheduler_io_pwrite(scheduler, io, OFFT2NUM(from), self, SIZET2NUM(length), SIZET2NUM(offset));
+        VALUE result = rb_fiber_scheduler_io_pwrite(scheduler, io, from, self, length, offset);
 
         if (!UNDEF_P(result)) {
             return result;
diff --git a/scheduler.c b/scheduler.c
index fb84e6b4ddba6b..477f11c03c32b7 100644
--- a/scheduler.c
+++ b/scheduler.c
@@ -458,19 +458,18 @@ VALUE rb_fiber_scheduler_io_selectv(VALUE scheduler, int argc, VALUE *argv)
 
 /*
  *  Document-method: Fiber::Scheduler#io_read
- *  call-seq: io_read(io, buffer, length) -> read length or -errno
+ *  call-seq: io_read(io, buffer, minimum_length) -> read length or -errno
  *
- *  Invoked by IO#read to read +length+ bytes from +io+ into a specified
- *  +buffer+ (see IO::Buffer).
+ *  Invoked by IO#read or IO#Buffer.read to read +length+ bytes from +io+ into a
+ *  specified +buffer+ (see IO::Buffer).
  *
- *  The +length+ argument is the "minimum length to be read".
- *  If the IO buffer size is 8KiB, but the +length+ is +1024+ (1KiB), up to
- *  8KiB might be read, but at least 1KiB will be.
- *  Generally, the only case where less data than +length+ will be read is if
- *  there is an error reading the data.
+ *  The +minimum_length+ argument is the "minimum length to be read". If the IO
+ *  buffer size is 8KiB, but the +length+ is +1024+ (1KiB), up to 8KiB might be
+ *  read, but at least 1KiB will be. Generally, the only case where less data
+ *  than +length+ will be read is if there is an error reading the data.
  *
- *  Specifying a +length+ of 0 is valid and means try reading at least once
- *  and return any available data.
+ *  Specifying a +length+ of 0 is valid and means try reading at least once and
+ *  return any available data.
  *
  *  Suggested implementation should try to read from +io+ in a non-blocking
  *  manner and call #io_wait if the +io+ is not ready (which will yield control
@@ -478,8 +477,8 @@ VALUE rb_fiber_scheduler_io_selectv(VALUE scheduler, int argc, VALUE *argv)
  *
  *  See IO::Buffer for an interface available to return data.
  *
- *  Expected to return number of bytes read, or, in case of an error, <tt>-errno</tt>
- *  (negated number corresponding to system's error code).
+ *  Expected to return number of bytes read, or, in case of an error,
+ *  <tt>-errno</tt> (negated number corresponding to system's error code).
  *
  *  The method should be considered _experimental_.
  */
@@ -513,28 +512,29 @@ rb_fiber_scheduler_io_pread(VALUE scheduler, VALUE io, rb_off_t from, VALUE buff
 
 /*
  *  Document-method: Scheduler#io_write
- *  call-seq: io_write(io, buffer, length) -> written length or -errno
+ *  call-seq: io_write(io, buffer, minimum_length) -> written length or -errno
  *
- *  Invoked by IO#write to write +length+ bytes to +io+ from
+ *  Invoked by IO#write or IO::Buffer#write to write +length+ bytes to +io+ from
  *  from a specified +buffer+ (see IO::Buffer).
  *
- *  The +length+ argument is the "(minimum) length to be written".
- *  If the IO buffer size is 8KiB, but the +length+ specified is 1024 (1KiB),
- *  at most 8KiB will be written, but at least 1KiB will be.
- *  Generally, the only case where less data than +length+ will be written is if
- *  there is an error writing the data.
+ *  The +minimum_length+ argument is the "minimum length to be written". If the
+ *  IO buffer size is 8KiB, but the +length+ specified is 1024 (1KiB), at most
+ *  8KiB will be written, but at least 1KiB will be. Generally, the only case
+ *  where less data than +minimum_length+ will be written is if there is an
+ *  error writing the data.
  *
- *  Specifying a +length+ of 0 is valid and means try writing at least once,
- *  as much data as possible.
+ *  Specifying a +length+ of 0 is valid and means try writing at least once, as
+ *  much data as possible.
  *
  *  Suggested implementation should try to write to +io+ in a non-blocking
  *  manner and call #io_wait if the +io+ is not ready (which will yield control
  *  to other fibers).
  *
- *  See IO::Buffer for an interface available to get data from buffer efficiently.
+ *  See IO::Buffer for an interface available to get data from buffer
+ *  efficiently.
  *
- *  Expected to return number of bytes written, or, in case of an error, <tt>-errno</tt>
- *  (negated number corresponding to system's error code).
+ *  Expected to return number of bytes written, or, in case of an error,
+ *  <tt>-errno</tt> (negated number corresponding to system's error code).
  *
  *  The method should be considered _experimental_.
  */
diff --git a/test/fiber/test_io_buffer.rb b/test/fiber/test_io_buffer.rb
index 48a34c31b6190a..3de70200d5c075 100644
--- a/test/fiber/test_io_buffer.rb
+++ b/test/fiber/test_io_buffer.rb
@@ -122,4 +122,37 @@ def test_write_nonblock
     i&.close
     o&.close
   end
+
+  def test_io_buffer_read_write
+    omit "UNIXSocket is not defined!" unless defined?(UNIXSocket)
+
+    i, o = UNIXSocket.pair
+    source_buffer = IO::Buffer.for("Hello World!")
+    destination_buffer = IO::Buffer.new(source_buffer.size)
+
+    # Test non-scheduler code path:
+    source_buffer.write(o, source_buffer.size)
+    destination_buffer.read(i, source_buffer.size)
+    assert_equal source_buffer, destination_buffer
+
+    # Test scheduler code path:
+    destination_buffer.clear
+
+    thread = Thread.new do
+      scheduler = IOBufferScheduler.new
+      Fiber.set_scheduler scheduler
+
+      Fiber.schedule do
+        source_buffer.write(o, source_buffer.size)
+        destination_buffer.read(i, source_buffer.size)
+      end
+    end
+
+    thread.join
+
+    assert_equal source_buffer, destination_buffer
+  ensure
+    i&.close
+    o&.close
+  end
 end