diff --git a/libexec/rbenv-init b/libexec/rbenv-init
index 8e6ee3d8..9fcfc2f4 100755
--- a/libexec/rbenv-init
+++ b/libexec/rbenv-init
@@ -33,7 +33,7 @@ done
 
 shell="$1"
 if [ -z "$shell" ]; then
-  shell="$(ps c -p "$PPID" -o 'ucomm=' 2>/dev/null || true)"
+  shell="$(ps -p "$PPID" -o 'args=' 2>/dev/null || true)"
   shell="${shell##-}"
   shell="${shell%% *}"
   shell="${shell:-$SHELL}"