diff --git a/runtime/indent/make.vim b/runtime/indent/make.vim
index 66a8a40..4483efd 100644
--- a/runtime/indent/make.vim
+++ b/runtime/indent/make.vim
@@ -20,8 +20,8 @@
 let s:rule_rx = '^[^ \t#:][^#:]*:\{1,2}\%([^=:]\|$\)'
 let s:continued_rule_rx = '^[^#:]*:\{1,2}\%([^=:]\|$\)'
 let s:continuation_rx = '\\$'
-let s:assignment_rx = '^\s*\h\w*\s*[+?]\==\s*\zs.*\\$'
-let s:folded_assignment_rx = '^\s*\h\w*\s*[+?]\=='
+let s:assignment_rx = '^\s*\h\w*\s*[+:?]\==\s*\zs.*\\$'
+let s:folded_assignment_rx = '^\s*\h\w*\s*[+:?]\=='
 " TODO: This needs to be a lot more restrictive in what it matches.
 let s:just_inserted_rule_rx = '^\s*[^#:]\+:\{1,2}$'
 let s:conditional_directive_rx = '^ *\%(ifn\=\%(eq\|def\)\|else\)\>'