diff --git a/clean_files.txt b/clean_files.txt
index 40dd3ed3..a7e70eb9 100644
--- a/clean_files.txt
+++ b/clean_files.txt
@@ -111,6 +111,9 @@ themes/command_duration.theme.bash
 themes/easy
 themes/modern
 themes/powerline
+themes/powerline-multiline
+themes/powerline-naked
+themes/powerline-plain
 themes/purity
 
 # vendor init files
diff --git a/themes/powerline-multiline/powerline-multiline.theme.bash b/themes/powerline-multiline/powerline-multiline.theme.bash
index a1663e6f..e15c3621 100644
--- a/themes/powerline-multiline/powerline-multiline.theme.bash
+++ b/themes/powerline-multiline/powerline-multiline.theme.bash
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 
 . "$BASH_IT/themes/powerline-multiline/powerline-multiline.base.bash"
 
diff --git a/themes/powerline-naked/powerline-naked.theme.bash b/themes/powerline-naked/powerline-naked.theme.bash
index 417ae71a..72c986ba 100644
--- a/themes/powerline-naked/powerline-naked.theme.bash
+++ b/themes/powerline-naked/powerline-naked.theme.bash
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 
 . "$BASH_IT/themes/powerline-naked/powerline-naked.base.bash"
 
diff --git a/themes/powerline-plain/powerline-plain.base.bash b/themes/powerline-plain/powerline-plain.base.bash
index ce91ef89..3326414d 100644
--- a/themes/powerline-plain/powerline-plain.base.bash
+++ b/themes/powerline-plain/powerline-plain.base.bash
@@ -1,61 +1,64 @@
+# shellcheck shell=bash
 . "$BASH_IT/themes/powerline/powerline.base.bash"
 
 function __powerline_left_segment {
-  local OLD_IFS="${IFS}"; IFS="|"
-  local params=( $1 )
-  IFS="${OLD_IFS}"
-  local pad_before_segment=" "
+	local OLD_IFS="${IFS}"
+	IFS="|"
+	local params=("$1")
+	IFS="${OLD_IFS}"
+	local pad_before_segment=" "
 
-  if [[ "${SEGMENTS_AT_LEFT}" -eq 0 ]]; then
-    if [[ "${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT}" -ne 0 ]]; then
-      pad_before_segment=""
-    fi
-  else
-    if [[ "${POWERLINE_COMPACT_AFTER_SEPARATOR}" -ne 0 ]]; then
-      pad_before_segment=""
-    fi
-    # Since the previous segment wasn't the last segment, add padding, if needed
-    #
-    if [[ "${POWERLINE_COMPACT_BEFORE_SEPARATOR}" -eq 0 ]]; then
-      LEFT_PROMPT+="$(set_color - ${LAST_SEGMENT_COLOR}) ${normal}"
-    fi
-  fi
+	if [[ "${SEGMENTS_AT_LEFT}" -eq 0 ]]; then
+		if [[ "${POWERLINE_COMPACT_BEFORE_FIRST_SEGMENT}" -ne 0 ]]; then
+			pad_before_segment=""
+		fi
+	else
+		if [[ "${POWERLINE_COMPACT_AFTER_SEPARATOR}" -ne 0 ]]; then
+			pad_before_segment=""
+		fi
+		# Since the previous segment wasn't the last segment, add padding, if needed
+		#
+		if [[ "${POWERLINE_COMPACT_BEFORE_SEPARATOR}" -eq 0 ]]; then
+			LEFT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR}") ${normal}"
+		fi
+	fi
 
-  LEFT_PROMPT+="$(set_color - ${params[1]})${pad_before_segment}${params[0]}${normal}"
-  LAST_SEGMENT_COLOR=${params[1]}
-  (( SEGMENTS_AT_LEFT += 1 ))
+	LEFT_PROMPT+="$(set_color - "${params[1]}")${pad_before_segment}${params[0]}${normal}"
+	LAST_SEGMENT_COLOR=${params[1]}
+	((SEGMENTS_AT_LEFT += 1))
 }
 
 function __powerline_prompt_command {
-  local last_status="$?" ## always the first
+	local last_status="$?" ## always the first
 
-  LEFT_PROMPT=""
-  SEGMENTS_AT_LEFT=0
-  LAST_SEGMENT_COLOR=""
-  PROMPT_AFTER="${POWERLINE_PROMPT_AFTER}"
+	LEFT_PROMPT=""
+	SEGMENTS_AT_LEFT=0
+	LAST_SEGMENT_COLOR=""
+	PROMPT_AFTER="${POWERLINE_PROMPT_AFTER}"
 
-  _save-and-reload-history "${HISTORY_AUTOSAVE:-0}"
+	_save-and-reload-history "${HISTORY_AUTOSAVE:-0}"
 
-  ## left prompt ##
-  for segment in $POWERLINE_PROMPT; do
-    local info="$(__powerline_${segment}_prompt)"
-    [[ -n "${info}" ]] && __powerline_left_segment "${info}"
-  done
+	## left prompt ##
+	for segment in $POWERLINE_PROMPT; do
+		local info="$(__powerline_"${segment}"_prompt)"
+		[[ -n "${info}" ]] && __powerline_left_segment "${info}"
+	done
 
-  [[ "${last_status}" -ne 0 ]] && __powerline_left_segment $(__powerline_last_status_prompt ${last_status})
+	# shellcheck disable=SC2046
+	[[ "${last_status}" -ne 0 ]] && __powerline_left_segment $(__powerline_last_status_prompt ${last_status})
 
-  if [[ -n "${LEFT_PROMPT}" ]] && [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT}" -eq 0 ]]; then
-    __powerline_left_last_segment_padding
-  fi
+	if [[ -n "${LEFT_PROMPT}" ]] && [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT}" -eq 0 ]]; then
+		__powerline_left_last_segment_padding
+	fi
 
-  if [[ "${POWERLINE_COMPACT_PROMPT}" -eq 0 ]]; then
-    LEFT_PROMPT+=" "
-  fi
+	if [[ "${POWERLINE_COMPACT_PROMPT}" -eq 0 ]]; then
+		LEFT_PROMPT+=" "
+	fi
 
-  PS1="${LEFT_PROMPT}${PROMPT_AFTER}"
+	PS1="${LEFT_PROMPT}${PROMPT_AFTER}"
 
-  ## cleanup ##
-  unset LAST_SEGMENT_COLOR \
-        LEFT_PROMPT \
-        SEGMENTS_AT_LEFT
+	## cleanup ##
+	unset LAST_SEGMENT_COLOR \
+		LEFT_PROMPT \
+		SEGMENTS_AT_LEFT
 }
diff --git a/themes/powerline-plain/powerline-plain.theme.bash b/themes/powerline-plain/powerline-plain.theme.bash
index 0b8f4f56..9ea6cde9 100644
--- a/themes/powerline-plain/powerline-plain.theme.bash
+++ b/themes/powerline-plain/powerline-plain.theme.bash
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 
 . "$BASH_IT/themes/powerline-plain/powerline-plain.base.bash"