diff --git a/RELEASES.md b/RELEASES.md
index b355367d..fe629206 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -20,6 +20,11 @@ Compiler
 --------
 - Input mappings will no longer emit the destination param as a dependency.
 
+Documentation
+-------------
+- `@mdash` macro now formally defines an argument, correcting errors in
+  newer versions of Texinfo (~v6.7).
+
 Linker
 ------
 - Remove exception for input map dependency processing (now that compiler no
diff --git a/doc/macros.texi b/doc/macros.texi
index cabdd541..45750c7a 100644
--- a/doc/macros.texi
+++ b/doc/macros.texi
@@ -36,7 +36,7 @@ TAME
 
 @c insert appropriate em dash for mode
 @ifnottex
-@macro mdash
+@macro mdash{_}
 @inlinefmtifelse{html, @inlineraw{html,—}, —}
 @end macro
 @end ifnottex