diff --git a/clean_files.txt b/clean_files.txt
index 8f9c173a29..93cb79b36a 100644
--- a/clean_files.txt
+++ b/clean_files.txt
@@ -165,6 +165,7 @@ themes/modern
 themes/norbu
 themes/pete
 themes/powerline
+themes/powerline-multiline
 themes/pure
 themes/purity
 
diff --git a/themes/powerline-multiline/powerline-multiline.base.bash b/themes/powerline-multiline/powerline-multiline.base.bash
index 64360e110a..2ccdfd4156 100644
--- a/themes/powerline-multiline/powerline-multiline.base.bash
+++ b/themes/powerline-multiline/powerline-multiline.base.bash
@@ -3,11 +3,7 @@
 # shellcheck source-path=SCRIPTDIR/../powerline
 source "${BASH_IT?}/themes/powerline/powerline.base.bash"
 
-function __powerline_last_status_prompt {
-	[[ "$1" -ne 0 ]] && echo "$(set_color ${LAST_STATUS_THEME_PROMPT_COLOR} -) ${1} ${normal}"
-}
-
-function __powerline_right_segment {
+function __powerline_right_segment() {
 	local -a params
 	IFS="|" read -ra params <<< "${1}"
 	local pad_before_segment=" "
@@ -17,92 +13,95 @@ function __powerline_right_segment {
 		if [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT}" -ne 0 ]]; then
 			pad_before_segment=""
 		fi
-		RIGHT_PROMPT+="$(set_color ${params[1]} -)${POWERLINE_RIGHT_END}${normal}"
+		RIGHT_PROMPT+="$(set_color "${params[1]:-}" -)${POWERLINE_RIGHT_END?}${normal?}"
 		((padding += 1))
 	else
-		if [[ "${POWERLINE_COMPACT_BEFORE_SEPARATOR}" -ne 0 ]]; then
+		if [[ "${POWERLINE_COMPACT_BEFORE_SEPARATOR:-}" -ne 0 ]]; then
 			pad_before_segment=""
 		fi
 		# Since the previous segment wasn't the last segment, add padding, if needed
 		#
-		if [[ "${POWERLINE_COMPACT_AFTER_SEPARATOR}" -eq 0 ]]; then
-			RIGHT_PROMPT+="$(set_color - ${LAST_SEGMENT_COLOR}) ${normal}"
+		if [[ "${POWERLINE_COMPACT_AFTER_SEPARATOR:-0}" -eq 0 ]]; then
+			RIGHT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR?}") ${normal}"
 			((padding += 1))
 		fi
-		if [[ "${LAST_SEGMENT_COLOR}" -eq "${params[1]}" ]]; then
-			RIGHT_PROMPT+="$(set_color - ${LAST_SEGMENT_COLOR})${POWERLINE_RIGHT_SEPARATOR_SOFT}${normal}"
+		if [[ "${LAST_SEGMENT_COLOR}" -eq "${params[1]:-}" ]]; then
+			RIGHT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR?}")${POWERLINE_RIGHT_SEPARATOR_SOFT?}${normal?}"
 		else
-			RIGHT_PROMPT+="$(set_color ${params[1]} ${LAST_SEGMENT_COLOR})${POWERLINE_RIGHT_SEPARATOR}${normal}"
+			RIGHT_PROMPT+="$(set_color "${params[1]:-}" "${LAST_SEGMENT_COLOR?}")${POWERLINE_RIGHT_SEPARATOR?}${normal?}"
 		fi
 		((padding += 1))
 	fi
 
-	RIGHT_PROMPT+="$(set_color - ${params[1]})${pad_before_segment}${params[0]}${normal}"
+	RIGHT_PROMPT+="$(set_color - "${params[1]:-}")${pad_before_segment}${params[0]}${normal?}"
 
 	((padding += ${#pad_before_segment}))
 	((padding += ${#params[0]}))
 
 	((RIGHT_PROMPT_LENGTH += padding))
-	LAST_SEGMENT_COLOR="${params[1]}"
+	LAST_SEGMENT_COLOR="${params[1]:-}"
 	((SEGMENTS_AT_RIGHT += 1))
 }
 
-function __powerline_right_first_segment_padding {
-	RIGHT_PROMPT+="$(set_color - ${LAST_SEGMENT_COLOR}) ${normal}"
+function __powerline_right_first_segment_padding() {
+	RIGHT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR?}") ${normal?}"
 	((RIGHT_PROMPT_LENGTH += 1))
 }
 
-function __powerline_prompt_command {
+function __powerline_last_status_prompt() {
+	[[ "$1" -ne 0 ]] && echo "$(set_color "${LAST_STATUS_THEME_PROMPT_COLOR?}" -) ${1} ${normal?}"
+}
+
+function __powerline_prompt_command() {
 	local last_status="$?" ## always the first
-	local move_cursor_rightmost='\033[500C'
+	local move_cursor_rightmost='\033[500C' info prompt
 
-	LEFT_PROMPT=""
-	RIGHT_PROMPT=""
-	RIGHT_PROMPT_LENGTH=${POWERLINE_PADDING}
-	SEGMENTS_AT_LEFT=0
-	SEGMENTS_AT_RIGHT=0
-	LAST_SEGMENT_COLOR=""
+	local LEFT_PROMPT=""
+	local RIGHT_PROMPT=""
+	local RIGHT_PROMPT_LENGTH=${POWERLINE_PADDING?}
+	local SEGMENTS_AT_LEFT=0
+	local SEGMENTS_AT_RIGHT=0
+	local LAST_SEGMENT_COLOR=""
 
 	_save-and-reload-history "${HISTORY_AUTOSAVE:-0}"
 
+	if [[ -n "${POWERLINE_PROMPT_DISTRO_LOGO:-}" ]]; then
+		LEFT_PROMPT+="$(set_color "${PROMPT_DISTRO_LOGO_COLOR?}" "${PROMPT_DISTRO_LOGO_COLORBG?}")${PROMPT_DISTRO_LOGO?}$(set_color - -)"
+	fi
+
 	## left prompt ##
-	for segment in $POWERLINE_LEFT_PROMPT; do
-		local info="$(__powerline_${segment}_prompt)"
+	for segment in ${POWERLINE_PROMPT-"user_info scm python_venv ruby node cwd"}; do
+		info="$("__powerline_${segment}_prompt")"
 		[[ -n "${info}" ]] && __powerline_left_segment "${info}"
 	done
 
-	if [[ -n "${LEFT_PROMPT}" ]] && [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT}" -eq 0 ]]; then
+	if [[ -n "${LEFT_PROMPT:-}" ]] && [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT:-0}" -eq 0 ]]; then
 		__powerline_left_last_segment_padding
 	fi
 
-	[[ -n "${LEFT_PROMPT}" ]] && LEFT_PROMPT+="$(set_color ${LAST_SEGMENT_COLOR} -)${POWERLINE_LEFT_END}${normal}"
+	[[ -n "${LEFT_PROMPT:-}" ]] && LEFT_PROMPT+="$(set_color "${LAST_SEGMENT_COLOR?}" -)${POWERLINE_LEFT_END?}${normal?}"
 
 	## right prompt ##
 	if [[ -n "${POWERLINE_RIGHT_PROMPT}" ]]; then
 		# LEFT_PROMPT+="${move_cursor_rightmost}"
 		for segment in $POWERLINE_RIGHT_PROMPT; do
-			local info="$(__powerline_${segment}_prompt)"
+			info="$("__powerline_${segment}_prompt")"
 			[[ -n "${info}" ]] && __powerline_right_segment "${info}"
 		done
 
-		if [[ -n "${RIGHT_PROMPT}" ]] && [[ "${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT}" -eq 0 ]]; then
+		if [[ -n "${RIGHT_PROMPT:-}" ]] && [[ "${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT:-0}" -eq 0 ]]; then
 			__powerline_right_first_segment_padding
 		fi
 
-		RIGHT_PAD=$(printf "%.s " $(seq 1 $RIGHT_PROMPT_LENGTH))
+		RIGHT_PAD=$(printf "%.s " $(seq 1 "${RIGHT_PROMPT_LENGTH}"))
 		LEFT_PROMPT+="${RIGHT_PAD}${move_cursor_rightmost}"
 		LEFT_PROMPT+="\033[$((${#RIGHT_PAD} - 1))D"
 	fi
 
-	local prompt="${PROMPT_CHAR}"
-	if [[ "${POWERLINE_COMPACT_PROMPT}" -eq 0 ]]; then
+	prompt="${PROMPT_CHAR?}"
+	if [[ "${POWERLINE_COMPACT_PROMPT:-0}" -eq 0 ]]; then
 		prompt+=" "
 	fi
 
-	PS1="${LEFT_PROMPT}${RIGHT_PROMPT}\n$(__powerline_last_status_prompt ${last_status})${prompt}"
-
-	## cleanup ##
-	unset LAST_SEGMENT_COLOR \
-		LEFT_PROMPT RIGHT_PROMPT RIGHT_PROMPT_LENGTH \
-		SEGMENTS_AT_LEFT SEGMENTS_AT_RIGHT
+	PS1="${LEFT_PROMPT}${RIGHT_PROMPT}\n$(__powerline_last_status_prompt "${last_status}")${prompt}"
 }
diff --git a/themes/powerline-multiline/powerline-multiline.theme.bash b/themes/powerline-multiline/powerline-multiline.theme.bash
index 48a1243e03..aa8c52cdf8 100644
--- a/themes/powerline-multiline/powerline-multiline.theme.bash
+++ b/themes/powerline-multiline/powerline-multiline.theme.bash
@@ -1,22 +1,23 @@
-#!/usr/bin/env bash
-
-. "$BASH_IT/themes/powerline-multiline/powerline-multiline.base.bash"
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+# shellcheck source-path=SCRIPTDIR/../powerline-multiline
+source "${BASH_IT?}/themes/powerline-multiline/powerline-multiline.base.bash"
 
 PROMPT_CHAR=${POWERLINE_PROMPT_CHAR:="❯"}
-POWERLINE_LEFT_SEPARATOR=${POWERLINE_LEFT_SEPARATOR:=""}
-POWERLINE_LEFT_SEPARATOR_SOFT=${POWERLINE_LEFT_SEPARATOR_SOFT:=""}
-POWERLINE_RIGHT_SEPARATOR=${POWERLINE_RIGHT_SEPARATOR:=""}
-POWERLINE_RIGHT_SEPARATOR_SOFT=${POWERLINE_RIGHT_SEPARATOR_SOFT:=""}
-POWERLINE_LEFT_END=${POWERLINE_LEFT_END:=""}
-POWERLINE_RIGHT_END=${POWERLINE_RIGHT_END:=""}
-POWERLINE_PADDING=${POWERLINE_PADDING:=2}
-
-POWERLINE_COMPACT=${POWERLINE_COMPACT:=0}
-POWERLINE_COMPACT_BEFORE_SEPARATOR=${POWERLINE_COMPACT_BEFORE_SEPARATOR:=${POWERLINE_COMPACT}}
-POWERLINE_COMPACT_AFTER_SEPARATOR=${POWERLINE_COMPACT_AFTER_SEPARATOR:=${POWERLINE_COMPACT}}
-POWERLINE_COMPACT_BEFOR_FIRST_SEGMENT=${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT:=${POWERLINE_COMPACT}}
-POWERLINE_COMPACT_AFTER_LAST_SEGMENT=${POWERLINE_COMPACT_AFTER_LAST_SEGMENT:=${POWERLINE_COMPACT}}
-POWERLINE_COMPACT_PROMPT=${POWERLINE_COMPACT_PROMPT:=${POWERLINE_COMPACT}}
+: "${POWERLINE_LEFT_SEPARATOR:=""}"
+: "${POWERLINE_LEFT_SEPARATOR_SOFT:=""}"
+: "${POWERLINE_RIGHT_SEPARATOR:=""}"
+: "${POWERLINE_RIGHT_SEPARATOR_SOFT:=""}"
+: "${POWERLINE_LEFT_END:=""}"
+: "${POWERLINE_RIGHT_END:=""}"
+: "${POWERLINE_PADDING:=2}"
+
+: "${POWERLINE_COMPACT:=0}"
+: "${POWERLINE_COMPACT_BEFORE_SEPARATOR:=${POWERLINE_COMPACT}}"
+: "${POWERLINE_COMPACT_AFTER_SEPARATOR:=${POWERLINE_COMPACT}}"
+: "${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT:=${POWERLINE_COMPACT}}"
+: "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT:=${POWERLINE_COMPACT}}"
+: "${POWERLINE_COMPACT_PROMPT:=${POWERLINE_COMPACT}}"
 
 USER_INFO_SSH_CHAR=${POWERLINE_USER_INFO_SSH_CHAR:=" "}
 USER_INFO_THEME_PROMPT_COLOR=${POWERLINE_USER_INFO_COLOR:=32}
@@ -67,12 +68,12 @@ LAST_STATUS_THEME_PROMPT_COLOR=${POWERLINE_LAST_STATUS_COLOR:=196}
 
 CLOCK_THEME_PROMPT_COLOR=${POWERLINE_CLOCK_COLOR:=240}
 
-BATTERY_AC_CHAR=${BATTERY_AC_CHAR:="⚡"}
+: "${BATTERY_AC_CHAR:="⚡"}"
 BATTERY_STATUS_THEME_PROMPT_GOOD_COLOR=${POWERLINE_BATTERY_GOOD_COLOR:=70}
 BATTERY_STATUS_THEME_PROMPT_LOW_COLOR=${POWERLINE_BATTERY_LOW_COLOR:=208}
 BATTERY_STATUS_THEME_PROMPT_CRITICAL_COLOR=${POWERLINE_BATTERY_CRITICAL_COLOR:=160}
 
-THEME_CLOCK_FORMAT=${THEME_CLOCK_FORMAT:="%H:%M:%S"}
+: "${THEME_CLOCK_FORMAT:="%H:%M:%S"}"
 
 IN_VIM_THEME_PROMPT_COLOR=${POWERLINE_IN_VIM_COLOR:=245}
 IN_VIM_THEME_PROMPT_TEXT=${POWERLINE_IN_VIM_TEXT:="vim"}
@@ -99,7 +100,7 @@ GCLOUD_CHAR=${POWERLINE_GCLOUD_CHAR:="❲G❳ "}
 
 COMMAND_DURATION_PROMPT_COLOR=${POWERLINE_COMMAND_DURATION_COLOR:=129}
 
-POWERLINE_LEFT_PROMPT=${POWERLINE_LEFT_PROMPT:="scm python_venv ruby node cwd"}
-POWERLINE_RIGHT_PROMPT=${POWERLINE_RIGHT_PROMPT:="in_vim clock battery user_info"}
+: "${POWERLINE_LEFT_PROMPT:="scm python_venv ruby node cwd"}"
+: "${POWERLINE_RIGHT_PROMPT:="in_vim clock battery user_info"}"
 
 safe_append_prompt_command __powerline_prompt_command