diff --git a/lib/std/io/stream/buffer.c3 b/lib/std/io/stream/buffer.c3
index eb44bc3c8..c158e2b5e 100644
--- a/lib/std/io/stream/buffer.c3
+++ b/lib/std/io/stream/buffer.c3
@@ -120,7 +120,7 @@ fn usz! WriteBuffer.write(&self, char[] bytes) @dynamic
 
 fn void! WriteBuffer.write_byte(&self, char c) @dynamic
 {
-	usz n = self.bytes.len - self.index - 1;
+	usz n = self.bytes.len - self.index;
 	if (n == 0)
 	{
 		self.write_pending()!;
diff --git a/test/unit/stdlib/io/bufferstream.c3 b/test/unit/stdlib/io/bufferstream.c3
index a40234c20..1443279bf 100644
--- a/test/unit/stdlib/io/bufferstream.c3
+++ b/test/unit/stdlib/io/bufferstream.c3
@@ -66,4 +66,29 @@ fn void! writebuffer()
     assert(n == DATA.len, "got %d; want %d", n, DATA.len);
     String got = out.str_view();
     assert(got == DATA, "got %s; want %s", got, DATA);
-}
\ No newline at end of file
+}
+
+fn void! writebuffer_write_byte()
+{
+    ByteWriter out;
+    out.temp_init();
+    char[2] buf;
+    WriteBuffer write_buf;
+    write_buf.init(&out, buf[..]);
+
+	write_buf.write_byte('a')!;
+	assert(write_buf.str_view() == "a");
+    assert(out.str_view() == "");
+
+	write_buf.write_byte('b')!;
+	assert(write_buf.str_view() == "ab");
+    assert(out.str_view() == "");
+
+	write_buf.write_byte('c')!;
+	assert(write_buf.str_view() == "c");
+    assert(out.str_view() == "ab");
+
+	write_buf.flush()!;
+	assert(write_buf.str_view() == "");
+    assert(out.str_view() == "abc");
+}