diff --git a/clean_files.txt b/clean_files.txt
index 1c205381ec..d8710bb593 100644
--- a/clean_files.txt
+++ b/clean_files.txt
@@ -160,6 +160,7 @@ themes/brainy
 themes/brunton
 themes/candy
 themes/clean
+themes/doubletime
 themes/easy
 themes/elixr
 themes/essential
diff --git a/themes/doubletime/doubletime.theme.bash b/themes/doubletime/doubletime.theme.bash
index 0c579e37f7..e60711aaf0 100644
--- a/themes/doubletime/doubletime.theme.bash
+++ b/themes/doubletime/doubletime.theme.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC2034,SC2154
 
 SCM_THEME_PROMPT_DIRTY=''
 SCM_THEME_PROMPT_CLEAN=''
@@ -7,23 +8,23 @@ SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
 SCM_HG_CHAR="${bold_red}☿${normal}"
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
-if [ ! -z $RVM_THEME_PROMPT_COLOR ]; then
-	RVM_THEME_PROMPT_COLOR=$(eval echo $$(echo ${RVM_THEME_PROMPT_COLOR}))
+if [[ -n "$RVM_THEME_PROMPT_COLOR" ]]; then
+	RVM_THEME_PROMPT_COLOR=$(eval "echo $$(echo ${RVM_THEME_PROMPT_COLOR})")
 else
 	RVM_THEME_PROMPT_COLOR="${red}"
 fi
 RVM_THEME_PROMPT_PREFIX="(${RVM_THEME_PROMPT_COLOR}rb${normal}: "
 RVM_THEME_PROMPT_SUFFIX=") "
-if [ ! -z $VIRTUALENV_THEME_PROMPT_COLOR ]; then
-	VIRTUALENV_THEME_PROMPT_COLOR=$(eval echo $$(echo ${VIRTUALENV_THEME_PROMPT_COLOR}))
+if [[ -n "$VIRTUALENV_THEME_PROMPT_COLOR" ]]; then
+	VIRTUALENV_THEME_PROMPT_COLOR=$(eval "echo $$(echo ${VIRTUALENV_THEME_PROMPT_COLOR})")
 else
 	VIRTUALENV_THEME_PROMPT_COLOR="${green}"
 fi
 VIRTUALENV_THEME_PROMPT_PREFIX="(${VIRTUALENV_THEME_PROMPT_COLOR}py${normal}: "
 VIRTUALENV_THEME_PROMPT_SUFFIX=") "
 
-if [ ! -z $THEME_PROMPT_HOST_COLOR ]; then
-	THEME_PROMPT_HOST_COLOR=$(eval echo $$(echo ${THEME_PROMPT_HOST_COLOR}))
+if [[ -n "$THEME_PROMPT_HOST_COLOR" ]]; then
+	THEME_PROMPT_HOST_COLOR=$(eval "echo $$(echo ${THEME_PROMPT_HOST_COLOR})")
 else
 	THEME_PROMPT_HOST_COLOR="$blue"
 fi