diff --git a/fix-kubectl b/fix-kubectl
index 18ce27e..7ed8440 100755
--- a/fix-kubectl
+++ b/fix-kubectl
@@ -4,21 +4,25 @@
 # - uneeded, as this checked whether script is sourced
 # SC1090 Can't follow non-constant source
 
+# User basename instead of ${0:##*/} to be POSIX compliant
+BASE_0=${BASE_0:-$(basename $0)}
+SCRIPT_DIR=${SCRIPT_DIR:-"$( cd -- "$( dirname -- "$0" )" &> /dev/null && pwd )"}
+BASE_SHELL=$(basename "$SHELL")
+
 # Helper function
 is_sourced() {
     if [ -n "$ZSH_VERSION" ]; then 
         case $ZSH_EVAL_CONTEXT in *:file:*) return 0;; esac
-    else  # Add additional POSIX-compatible shell names here, if needed.
-        case ${0##*/} in dash|-dash|bash|-bash|ksh|-ksh|sh|-sh) return 0;; esac
+    else
+        # case ${0##*/} in dash|-dash|bash|-bash|ksh|-ksh|sh|-sh) return 0;; esac
+        case "$(basename $0)" in $BASE_SHELL|-$BASE_SHELL) return 0;; esac
     fi
     return 1; # NOT sourced.
 }
 
-BASE_0=${BASE_0:-$0}
-BASE_SHELL=$(basename "$SHELL")
 if is_sourced; then
+    # This part is sourced, and might run in a non-bash shell
     DBG_="Is Sourced"
-    SCRIPT_DIR=$( cd -- "$( dirname -- "${BASE_0}" )" &> /dev/null && pwd )
     USER_HOME=$HOME
     [[ -n "${SUDO_USER}" ]] && USER_HOME="$(eval "echo ~${SUDO_USER}")"
 
@@ -101,7 +105,7 @@ if is_sourced; then
         }
     fi
 elif [[ "$1" == '-' ]]; then
-    printf 'BASE_0="%s"\n' "${BASE_0}"
+    printf 'BASE_0="%s"\nSCRIPT_DIR=%s\n' "${BASE_0}" "${SCRIPT_DIR}"
     cat "${BASH_SOURCE[0]}"
 else
     SCRIPT_NAME="$BASE_0"