diff --git a/highlighters/main/main-highlighter.zsh b/highlighters/main/main-highlighter.zsh
index 1e0af52..f3cfe43 100644
--- a/highlighters/main/main-highlighter.zsh
+++ b/highlighters/main/main-highlighter.zsh
@@ -127,20 +127,43 @@ _zsh_highlight_main_calculate_fallback() {
 #
 # Takes a single argument.
 #
+# Uses the following caller variables: [[ $this_word == *':alias:'* ]]
+#
 # The result will be stored in REPLY.
 _zsh_highlight_main__type() {
+  # Our caller knows whether aliases are allowed at this point.  Compare:
+  #    % ls
+  #    % sudo ls
+  if [[ $this_word == *':alias:'* ]]; then
+    integer -r aliases_allowed=1
+  else
+    integer -r aliases_allowed=0
+  fi
+  # For the same reason, we won't cache replies of anything that exists as an
+  # alias at all, regardless of $aliases_allowed.
+  #
+  # ### We probably _should_ cache them in a cache that's keyed on the value of
+  # ### $aliases_allowed, on the assumption that aliases are the common case.
+  integer may_cache=1
+
+  # Cache lookup
   if (( $+_zsh_highlight_main__command_type_cache )); then
     REPLY=$_zsh_highlight_main__command_type_cache[(e)$1]
     if [[ -n "$REPLY" ]]; then
       return
     fi
   fi
+
+  # Main logic
   if (( $#options_to_set )); then
     setopt localoptions $options_to_set;
   fi
   unset REPLY
   if zmodload -e zsh/parameter; then
     if (( $+aliases[(e)$1] )); then
+      may_cache=0
+    fi
+    if (( $+aliases[(e)$1] )) && (( aliases_allowed )); then
       REPLY=alias
     elif (( $+saliases[(e)${1##*.}] )); then
       REPLY='suffix alias'
@@ -165,9 +188,21 @@ _zsh_highlight_main__type() {
   fi
   if ! (( $+REPLY )); then
     # Note that 'type -w' will run 'rehash' implicitly.
-    REPLY="${$(LC_ALL=C builtin type -w -- $1 2>/dev/null)##*: }"
+    #
+    # We 'unalias' in a subshell, so the parent shell is not affected.
+    #
+    # The colon command is there just to avoid a command substitution that
+    # starts with an arithmetic expression [«((…))» as the first thing inside
+    # «$(…)»], which is area that has had some parsing bugs before 5.6
+    # (approximately).
+    REPLY="${$(:; (( aliases_allowed )) || unalias -- $1;LC_ALL=C builtin type -w -- $1 2>/dev/null)##*: }"
+    if [[ $REPLY == 'alias' ]]; then
+      may_cache=0
+    fi
   fi
-  if (( $+_zsh_highlight_main__command_type_cache )); then
+
+  # Cache population
+  if (( may_cache )) && (( $+_zsh_highlight_main__command_type_cache )); then
     _zsh_highlight_main__command_type_cache[(e)$1]=$REPLY
   fi
 }
diff --git a/highlighters/main/test-data/alias-after-precommand.zsh b/highlighters/main/test-data/alias-after-precommand.zsh
new file mode 100644
index 0000000..6a71759
--- /dev/null
+++ b/highlighters/main/test-data/alias-after-precommand.zsh
@@ -0,0 +1,42 @@
+#!/usr/bin/env zsh
+# -------------------------------------------------------------------------------------------------
+# Copyright (c) 2018 zsh-syntax-highlighting contributors
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without modification, are permitted
+# provided that the following conditions are met:
+#
+#  * Redistributions of source code must retain the above copyright notice, this list of conditions
+#    and the following disclaimer.
+#  * Redistributions in binary form must reproduce the above copyright notice, this list of
+#    conditions and the following disclaimer in the documentation and/or other materials provided
+#    with the distribution.
+#  * Neither the name of the zsh-syntax-highlighting contributors nor the names of its contributors
+#    may be used to endorse or promote products derived from this software without specific prior
+#    written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+# FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+# IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# -------------------------------------------------------------------------------------------------
+# -*- mode: zsh; sh-indentation: 2; indent-tabs-mode: nil; sh-basic-offset: 2; -*-
+# vim: ft=zsh sw=2 ts=2 et
+# -------------------------------------------------------------------------------------------------
+
+alias ls='ls -l'
+BUFFER=$'ls; sudo ls; noglob ls'
+
+expected_region_highlight=(
+  '1 2 alias' # ls
+  '3 3 commandseparator' # ;
+  '5 8 precommand' # sudo
+  '10 11 command' # ls
+  '12 12 commandseparator' # ;
+  '14 19 precommand' # noglob
+  '21 22 alias' # ls
+)