diff --git a/powerlevel9k.zsh-theme b/powerlevel9k.zsh-theme
index 2870802b..3d2d5d2c 100755
--- a/powerlevel9k.zsh-theme
+++ b/powerlevel9k.zsh-theme
@@ -19,9 +19,30 @@
 
 # Check if the theme was called as a function.
 if [[ $(whence -w prompt_powerlevel9k_setup) =~ "function" ]]; then
-  # Script is a function! We assume this to happen only in
-  # prezto, as they use the zstyle-builtin to set the theme.
-  0="${ZDOTDIR:-$HOME}/.zprezto/modules/prompt/functions/prompt_powerlevel9k_setup"
+  autoload -U is-at-least
+  if is-at-least 5.0.8; then
+    # Try to find the correct path of the script.
+    0=$(whence -v $0 | sed "s/$0 is a shell function from //")
+  elif [[ -f "${ZDOTDIR:-$HOME}/.zprezto/modules/prompt/init.zsh" ]]; then
+    # If there is an prezto installation, we assume that powerlevel9k is linked there.
+    0="${ZDOTDIR:-$HOME}/.zprezto/modules/prompt/functions/prompt_powerlevel9k_setup"
+  else
+    # Fallback: specify an installation path!
+    if [[ -z "$POWERLEVEL9K_INSTALLATION_PATH" ]]; then
+      print -P "%F{red}We could not locate the installation path of powerlevel9k.%f"
+      print -P "Please specify by setting %F{blue}POWERLEVEL9K_INSTALLATION_PATH%f (full path incl. file name) at the very beginning of your ~/.zshrc"
+      return 1
+    elif [[ -L "$POWERLEVEL9K_INSTALLATION_PATH" ]]; then
+      # Symlink
+      0="$POWERLEVEL9K_INSTALLATION_PATH"
+    elif [[ -f "$POWERLEVEL9K_INSTALLATION_PATH" ]]; then
+      # File
+      0="$POWERLEVEL9K_INSTALLATION_PATH"
+    elif [[ -d "$POWERLEVEL9K_INSTALLATION_PATH" ]]; then
+      # Directory
+      0="${POWERLEVEL9K_INSTALLATION_PATH}/powerlevel9k.zsh-theme"
+    fi
+  fi
 fi
 
 # Check if filename is a symlink.
@@ -33,7 +54,7 @@ elif [[ -f $0 ]]; then
   filename="$0"
 else
   print -P "%F{red}Script location could not be found!%f"
-  exit 1
+  return 1
 fi
 script_location="$(dirname $filename)"