diff --git a/lib/std/io/stream/buffer.c3 b/lib/std/io/stream/buffer.c3
index 1c106bf46..eb44bc3c8 100644
--- a/lib/std/io/stream/buffer.c3
+++ b/lib/std/io/stream/buffer.c3
@@ -120,14 +120,17 @@ fn usz! WriteBuffer.write(&self, char[] bytes) @dynamic
 
 fn void! WriteBuffer.write_byte(&self, char c) @dynamic
 {
-	usz n = self.bytes.len - self.index;
-	if (n == 0) self.write_pending()!;
-	self.bytes[0] = c;
-	self.index = 1;
+	usz n = self.bytes.len - self.index - 1;
+	if (n == 0)
+	{
+		self.write_pending()!;
+	}
+	self.bytes[self.index] = c;
+	self.index += 1;
 }
 
 fn void! WriteBuffer.write_pending(&self) @local
 {
 	self.index -= self.wrapped_stream.write(self.bytes[:self.index])!;
 	if (self.index != 0) return IoError.INCOMPLETE_WRITE?;
-}
\ No newline at end of file
+}
diff --git a/releasenotes.md b/releasenotes.md
index 5aae05569..e5718f2ad 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -9,6 +9,7 @@
 ### Fixes
 - Fix bug where `a > 0 ? f() : g()` could cause a compiler crash if both returned `void!`.
 - `@builtin` was not respected for generic modules #1617.
+- Fix issue writing a single byte in the WriteBuffer
 
 ### Stdlib changes