--- a/old-configure.in
+++ b/old-configure.in
@@ -2323,19 +2323,16 @@ if test -n "$MOZ_GRAPHENE"; then
     AC_DEFINE(MOZ_GRAPHENE)
 fi
 
 if test -n "$MOZ_MULET"; then
     AC_DEFINE(MOZ_MULET)
 fi
 
 # Propagate feature switches for code written in rust from confvars.sh
-if test -n "$MOZ_RUST_MP4PARSE"; then
-    AC_DEFINE(MOZ_RUST_MP4PARSE)
-fi
 if test -n "$MOZ_RUST_URLPARSE"; then
     AC_DEFINE(MOZ_RUST_URLPARSE)
     AC_SUBST(MOZ_RUST_URLPARSE)
 fi
 
 AC_SUBST(MOZ_PHOENIX)
 AC_SUBST(MOZ_XULRUNNER)
 AC_SUBST(MOZ_B2G)