diff --git a/bashrc b/bashrc
index 711cc96..4597e9b 100644
--- a/bashrc
+++ b/bashrc
@@ -13,8 +13,8 @@ HISTSIZE=100000
 HISTFILE=~/.bash_history
 shopt -s histappend
 
+PROMPT_COMMAND="history -a; history -c; history -r"
 . ~/etc/liquidprompt/liquidprompt
-PROMPT_COMMAND="$PROMPT_COMMAND; history -a; history -c; history -r"
 
 shopt -s autocd
 
diff --git a/liquid.ps1 b/liquid.ps1
index 927c8dc..2c86449 100644
--- a/liquid.ps1
+++ b/liquid.ps1
@@ -49,7 +49,7 @@ LP_TITLE="$(_lp_title "$LP_PS1")"
 # Insert it in the prompt
 LP_PS1="${LP_TITLE}${LP_PS1}"
 
-if [ -n "${IN_NIX_SHELL}" ]; then
+if [[ -n "${IN_NIX_SHELL}" ]]; then
     LP_PS1="${LP_COLOR_NIX_SHELL}[nix-shell]${NO_COL} ${LP_PS1}"
 fi