diff --git a/gitprompt.sh b/gitprompt.sh
index 98c7696..ed60902 100755
--- a/gitprompt.sh
+++ b/gitprompt.sh
@@ -1,14 +1,13 @@
 #!/bin/sh
 
-function async_run()
+function async_run() 
 {
   {
     eval "$@" &> /dev/null
   }&
 }
 
-function git_prompt_dir()
-{
+function git_prompt_dir() {
   # assume the gitstatus.sh is in the same directory as this script
   # code thanks to http://stackoverflow.com/questions/59895
   if [ -z "$__GIT_PROMPT_DIR" ]; then
@@ -23,11 +22,10 @@ function git_prompt_dir()
 }
 
 function echoc() {
-    echo -e "${1}$2${ResetColor}" | sed 's/\\\]//g'  | sed 's/\\\[//g'
+  echo -e "${1}$2${ResetColor}" | sed 's/\\\]//g'  | sed 's/\\\[//g'
 }
 
-function get_theme()
-{
+function get_theme() {
   local CUSTOM_THEME_FILE="${HOME}/.git-prompt-colors.sh"
   local DEFAULT_THEME_FILE="${__GIT_PROMPT_DIR}/themes/Default.bgptheme"
 
@@ -67,16 +65,15 @@ function get_theme()
   fi
 }
 
-function git_prompt_load_theme()
-{
+function git_prompt_load_theme() {
+  git_prompt_reset
   get_theme
   local DEFAULT_THEME_FILE="${__GIT_PROMPT_DIR}/themes/Default.bgptheme"
   source "${DEFAULT_THEME_FILE}"
   source "${__GIT_PROMPT_THEME_FILE}"
 }
 
-function git_prompt_list_themes()
-{
+function git_prompt_list_themes() {
   local oldTheme
   local oldThemeFile
 
@@ -160,7 +157,7 @@ function gp_set_file_var() {
 # return 0 (true) if any FILEPATH is readable, set ENVAR to it
 # return 1 (false) if not
 
-function gp_maybe_set_envar_to_path(){
+function gp_maybe_set_envar_to_path() {
   local envar="$1"
   shift
   local file
@@ -183,6 +180,7 @@ git_prompt_reset() {
   for var in GIT_PROMPT_DIR __GIT_PROMPT_COLORS_FILE __PROMPT_COLORS_FILE __GIT_STATUS_CMD GIT_PROMPT_THEME_NAME; do
     unset $var
   done
+  unset -f prompt_callback
 }
 
 # gp_format_exit_status RETVAL
@@ -203,8 +201,7 @@ gp_format_exit_status() {
     fi
 }
 
-function git_prompt_config()
-{
+function git_prompt_config() {
   #Checking if root to change output
   _isroot=false
   [[ $UID -eq 0 ]] && _isroot=true
@@ -225,10 +222,10 @@ function git_prompt_config()
 
   git_prompt_load_theme
 
-  if [ "`type -t prompt_callback`" = 'function' ]; then
-      prompt_callback="prompt_callback"
+  if is_function prompt_callback; then
+    prompt_callback="prompt_callback"
   else
-      prompt_callback="prompt_callback_default"
+    prompt_callback="prompt_callback_default"
   fi
 
   if [ $GIT_PROMPT_LAST_COMMAND_STATE = 0 ]; then
@@ -369,42 +366,42 @@ function setGitPrompt() {
 _have_find_mmin=1
 
 function olderThanMinutes() {
-    local matches
-    local find_exit_code
-
-    if [[ -z "$_find_command" ]]; then
-        if command -v gfind > /dev/null; then
-            _find_command=gfind
-        else
-            _find_command=find
-        fi
-    fi
+  local matches
+  local find_exit_code
 
-    if [[ "$_have_find_mmin" = 1 ]]; then
-        matches=`"$_find_command" "$1" -mmin +"$2" 2> /dev/null`
-        find_exit_code="$?"
-        if [[ -n "$matches" ]]; then
-            return 0
-        else
-            if [[ "$find_exit_code" != 0 ]]; then
-                _have_find_mmin=0
-            else
-                return 1
-            fi
-        fi
+  if [[ -z "$_find_command" ]]; then
+    if command -v gfind > /dev/null; then
+      _find_command=gfind
+    else
+      _find_command=find
     fi
+  fi
 
-    # try perl, solaris ships with perl
-    if command -v perl > /dev/null; then
-        perl -e '((time - (stat("'"$1"'"))[9]) / 60) > '"$2"' && exit(0) || exit(1)'
-        return "$?"
+  if [[ "$_have_find_mmin" = 1 ]]; then
+    matches=`"$_find_command" "$1" -mmin +"$2" 2> /dev/null`
+    find_exit_code="$?"
+    if [[ -n "$matches" ]]; then
+      return 0
     else
-        echo >&2
-        echo "WARNING: neither a find that supports -mmin (such as GNU find) or perl is available, disabling remote status checking. Install GNU find as gfind or perl to enable this feature, or set GIT_PROMPT_FETCH_REMOTE_STATUS=0 to disable this warning." >&2
-        echo >&2
-        GIT_PROMPT_FETCH_REMOTE_STATUS=0
+      if [[ "$find_exit_code" != 0 ]]; then
+        _have_find_mmin=0
+      else
         return 1
+      fi
     fi
+  fi
+
+  # try perl, solaris ships with perl
+  if command -v perl > /dev/null; then
+    perl -e '((time - (stat("'"$1"'"))[9]) / 60) > '"$2"' && exit(0) || exit(1)'
+    return "$?"
+  else
+    echo >&2
+    echo "WARNING: neither a find that supports -mmin (such as GNU find) or perl is available, disabling remote status checking. Install GNU find as gfind or perl to enable this feature, or set GIT_PROMPT_FETCH_REMOTE_STATUS=0 to disable this warning." >&2
+    echo >&2
+    GIT_PROMPT_FETCH_REMOTE_STATUS=0
+    return 1
+  fi
 }
 
 function checkUpstream() {
@@ -524,8 +521,14 @@ function updatePrompt() {
   PS1="${NEW_PROMPT//_LAST_COMMAND_INDICATOR_/${LAST_COMMAND_INDICATOR}}"
 }
 
+# Use exit status from declare command to determine whether input argument is a
+# bash function
+function is_function {
+  declare -Ff "$1" >/dev/null;
+}
+
 function prompt_callback_default {
-    return
+  return
 }
 
 function gp_install_prompt {