Fixed header
diff --git a/5.0/decoder.md b/5.0/decoder.md
index e9d5e2b..07e5725 100644
--- a/5.0/decoder.md
+++ b/5.0/decoder.md
@@ -321,7 +321,7 @@
 decoding* and *synchronous parsing*. In both settings, both the source and target sides are provided
 as input, and the decoder finds a derivation between them.
 
-### Constrained decoding
+#### Constrained decoding
 
 To enable constrained decoding, simply append the desired target string as part of the input, in
 the following format: