diff --git a/highlighters/main/main-highlighter.zsh b/highlighters/main/main-highlighter.zsh
index 9ac15e9..038215d 100644
--- a/highlighters/main/main-highlighter.zsh
+++ b/highlighters/main/main-highlighter.zsh
@@ -663,8 +663,15 @@ _zsh_highlight_main_highlighter_highlight_list()
           next_word+=':sudo_opt:'
         elif [[ $arg == '-'* ]]; then
           # Unknown flag.  We don't know whether it takes an argument or not,
-          # so we don't modify $next_word.
+          # so modify $next_word as we do for flags that require no argument.
+          # With that behaviour, if the flag in fact takes no argument we'll
+          # highlight the inner command word correctly, and if it does take an
+          # argument we'll highlight the command word correctly if the argument
+          # was given in the same shell word as the flag (as in '-uphy1729' or
+          # '--user=phy1729' without spaces).
           this_word=':sudo_opt:'
+          next_word+=':start:'
+          next_word+=':sudo_opt:'
         else
           # Not an option flag; nothing to do.  (If the command line is
           # syntactically valid, ${this_word//:sudo_opt:/} should be
diff --git a/highlighters/main/test-data/precommand-unknown-option.zsh b/highlighters/main/test-data/precommand-unknown-option.zsh
index cd94233..6baf9ff 100644
--- a/highlighters/main/test-data/precommand-unknown-option.zsh
+++ b/highlighters/main/test-data/precommand-unknown-option.zsh
@@ -39,5 +39,5 @@ expected_region_highlight=(
   '12 12 commandseparator' # ;
   '14 17 precommand' # sudo
   '19 20 single-hyphen-option' # -x
-  '22 23 default' # ls
+  '22 23 command' # ls
 )
diff --git a/highlighters/main/test-data/sudo-longopt.zsh b/highlighters/main/test-data/sudo-longopt.zsh
index 7a2ea9d..697f555 100644
--- a/highlighters/main/test-data/sudo-longopt.zsh
+++ b/highlighters/main/test-data/sudo-longopt.zsh
@@ -33,5 +33,5 @@ BUFFER='sudo --askpass ls'
 expected_region_highlight=(
   '1 4 precommand' # sudo
   '6 14 double-hyphen-option' # --askpass
-  '16 17 default' # ls (we don't know whether --askpass takes an argument)
+  '16 17 command' # ls (we don't know whether --askpass takes an argument)
 )