diff --git a/modules/haskell/init.zsh b/modules/haskell/init.zsh
index c1c78ca2a0..cb76864122 100644
--- a/modules/haskell/init.zsh
+++ b/modules/haskell/init.zsh
@@ -10,8 +10,11 @@ if (( ! $+commands[ghc] )); then
   return 1
 fi
 
+# Load dependencies.
+pmodload 'helper'
+
 # Prepend Cabal per user directories to PATH.
-if [[ "$OSTYPE" == darwin* && -d $HOME/Library/Haskell ]]; then
+if is-darwin && [[  -d $HOME/Library/Haskell ]]; then
   path=($HOME/Library/Haskell/bin(/N) $path)
 else
   path=($HOME/.cabal/bin(/N) $path)
diff --git a/modules/helper/init.zsh b/modules/helper/init.zsh
index 328bed4f71..6e83f89a18 100644
--- a/modules/helper/init.zsh
+++ b/modules/helper/init.zsh
@@ -29,3 +29,23 @@ function coalesce {
   done
   return 1
 }
+
+# is true on MacOS Darwin
+function is-darwin {
+  [[ "$OSTYPE" == darwin* ]]
+}
+
+# is true on Linux's
+function is-linux {
+  [[ "$OSTYPE" == linux* ]]
+}
+
+# is true on BSD's
+function is-bsd {
+  [[ "$OSTYPE" == *bsd* ]]
+}
+
+# is true on Cygwin (Windows)
+function is-cygwin {
+  [[ "$OSTYPE" == cygwin* ]]
+}
diff --git a/modules/homebrew/init.zsh b/modules/homebrew/init.zsh
index 9f7e0b4646..6605426f4f 100644
--- a/modules/homebrew/init.zsh
+++ b/modules/homebrew/init.zsh
@@ -6,7 +6,7 @@
 #
 
 # Return if requirements are not found.
-if [[ "$OSTYPE" != (darwin|linux)* ]]; then
+if ! is-darwin || ! is-linux; then
   return 1
 fi
 
diff --git a/modules/macports/init.zsh b/modules/macports/init.zsh
index d55744a875..7bf4ab2940 100644
--- a/modules/macports/init.zsh
+++ b/modules/macports/init.zsh
@@ -6,8 +6,11 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Load dependencies.
+pmodload 'helper'
+
 # Return if requirements are not found.
-if [[ "$OSTYPE" != darwin* ]]; then
+if ! is-darwin; then
   return 1
 fi
 
diff --git a/modules/osx/init.zsh b/modules/osx/init.zsh
index f7871ca718..62f219437b 100644
--- a/modules/osx/init.zsh
+++ b/modules/osx/init.zsh
@@ -5,8 +5,11 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Load dependencies.
+pmodload 'helper'
+
 # Return if requirements are not found.
-if [[ "$OSTYPE" != darwin* ]]; then
+if ! is-darwin; then
   return 1
 fi
 
diff --git a/modules/perl/init.zsh b/modules/perl/init.zsh
index b7a794797a..8f097f6cac 100644
--- a/modules/perl/init.zsh
+++ b/modules/perl/init.zsh
@@ -10,6 +10,9 @@ if (( ! $+commands[perl] )); then
   return 1
 fi
 
+# Load dependencies.
+pmodload 'helper'
+
 #
 # Load Perlbrew or plenv
 #
@@ -37,7 +40,7 @@ fi
 # Local Module Installation
 #
 
-if [[ "$OSTYPE" == darwin* ]]; then
+if is-darwin; then
   # Perl is slow; cache its output.
   cache_file="${TMPDIR:-/tmp}/prezto-perl-cache.$UID.zsh"
   perl_path="$HOME/Library/Perl/5.12"
diff --git a/modules/prompt/external/powerlevel10k b/modules/prompt/external/powerlevel10k
index 7306efb94b..6a0e7523b2 160000
--- a/modules/prompt/external/powerlevel10k
+++ b/modules/prompt/external/powerlevel10k
@@ -1 +1 @@
-Subproject commit 7306efb94ba739f714972038ad74c48d2bebfdd6
+Subproject commit 6a0e7523b232d02854008405a3645031c848922b
diff --git a/modules/prompt/functions/prompt_sorin_setup b/modules/prompt/functions/prompt_sorin_setup
index 41ac7d0175..a7d341ee8d 100644
--- a/modules/prompt/functions/prompt_sorin_setup
+++ b/modules/prompt/functions/prompt_sorin_setup
@@ -54,6 +54,13 @@ function prompt_sorin_async_callback {
         zle && zle reset-prompt
       fi
       ;;
+    "[async]")
+      # Code is 1 for corrupted worker output and 2 for dead worker.
+      if [[ $2 -eq 2 ]]; then
+	  # Our worker died unexpectedly.
+          typeset -g prompt_prezto_async_init=0
+      fi
+      ;;
   esac
 }
 
diff --git a/modules/python/init.zsh b/modules/python/init.zsh
index e5967f7aa8..809ab406e9 100644
--- a/modules/python/init.zsh
+++ b/modules/python/init.zsh
@@ -7,6 +7,9 @@
 #   Patrick Bos <egpbos@gmail.com>
 #
 
+# Load dependencies
+pmodload 'helper'
+
 # Load manually installed pyenv into the path
 if [[ -s "${PYENV_ROOT:=$HOME/.pyenv}/bin/pyenv" ]]; then
   path=("${PYENV_ROOT}/bin" $path)
@@ -22,7 +25,7 @@ elif (( $+commands[pyenv] )); then
 else
   if [[ -n "$PYTHONUSERBASE" ]]; then
     path=($PYTHONUSERBASE/bin $path)
-  elif [[ "$OSTYPE" == darwin* ]]; then
+  elif is-darwin; then
     path=($HOME/Library/Python/*/bin(N) $path)
   else
     # This is subject to change.
diff --git a/modules/rsync/init.zsh b/modules/rsync/init.zsh
index b3010ede32..79432c1251 100644
--- a/modules/rsync/init.zsh
+++ b/modules/rsync/init.zsh
@@ -10,6 +10,9 @@ if (( ! $+commands[rsync] )); then
   return 1
 fi
 
+# Load dependencies.
+pmodload 'helper'
+
 #
 # Aliases
 #
@@ -23,7 +26,7 @@ fi
 
 # macOS and HFS+ Enhancements
 # https://bombich.com/kb/ccc5/credits
-if [[ "$OSTYPE" == darwin* ]] && grep -q 'file-flags' <(rsync --help 2>&1); then
+if is-darwin && grep -q 'file-flags' <(rsync --help 2>&1); then
   _rsync_cmd="${_rsync_cmd} --crtimes --fileflags --protect-decmpfs --force-change"
 fi
 
diff --git a/modules/utility/init.zsh b/modules/utility/init.zsh
index a2e5c2bdfe..caa0ec8d41 100644
--- a/modules/utility/init.zsh
+++ b/modules/utility/init.zsh
@@ -134,9 +134,9 @@ if zstyle -t ':prezto:module:utility:grep' color; then
 fi
 
 # macOS Everywhere
-if [[ "$OSTYPE" == darwin* ]]; then
+if is-darwin; then
   alias o='open'
-elif [[ "$OSTYPE" == cygwin* ]]; then
+elif is-cygwin; then
   alias o='cygstart'
   alias pbcopy='tee > /dev/clipboard'
   alias pbpaste='cat /dev/clipboard'
@@ -166,7 +166,7 @@ fi
 alias df='df -kh'
 alias du='du -kh'
 
-if [[ "$OSTYPE" == (darwin*|*bsd*) ]]; then
+if is-darwin || is-bsd; then
   alias topc='top -o cpu'
   alias topm='top -o vsize'
 else