diff --git a/lisp/patch-quicklisp.lisp b/lisp/patch-quicklisp.lisp
index c892cb5..8aaadc0 100644
--- a/lisp/patch-quicklisp.lisp
+++ b/lisp/patch-quicklisp.lisp
@@ -35,7 +35,6 @@
 
 (defun roswell-installable-searcher (system-name)
   (let ((name (roswell-installed-system-name system-name))
-        (env "ROSINSTALL")
         pname)
     (and
      name
@@ -43,13 +42,12 @@
             (asdf:find-system pname nil)))
      (prog1
          (or (quicklisp-client:local-projects-searcher name)
-             (unless (find system-name (loop for ar = (ros:getenv env) then (subseq ar (1+ p))
+             (unless (find system-name (loop for ar = (ros:getenv "ROSINSTALL") then (subseq ar (1+ p))
                                              for p = (position #\, ar)
                                              for arg = (if p (subseq ar 0 p) ar)
                                              collect arg
                                              while p)
                            :test 'equal)
-               (roswell.util:setenv env (format nil "~A,~A" system-name (ros:getenv env)))
                (roswell:roswell `("install" ,system-name))
                (quicklisp-client:register-local-projects)
                (quicklisp-client:local-projects-searcher name))
diff --git a/lisp/util-install.lisp b/lisp/util-install.lisp
index 5254207..465b6ba 100644
--- a/lisp/util-install.lisp
+++ b/lisp/util-install.lisp
@@ -9,6 +9,7 @@
 (in-package :roswell.install)
 
 (defvar *ros-path* nil)
+(defvar *env* "ROSINSTALL")
 (defvar *checkout-default* 'checkout-github)
 
 (defun install-impl (impl version argv cmds)
@@ -43,7 +44,8 @@
 (defun install-system-if-probed (imp)
   (let ((result (or (read-call "ql-dist:find-system" imp)
                     (read-call "ql:where-is-system" imp))))
-    (when result
+    (when (and result
+               (= 1 (count #\, (ros:getenv *env*))))
       (funcall 'install-system-script imp)
       result)))
 
@@ -114,6 +116,7 @@
     with *ros-path* = (make-pathname :defaults (opt "argv0"))
     with _
     with changed
+    with envold = (ros:getenv *env*)
     for impl/version/tag = (first argv)
     for pos = (position #\/ impl/version/tag)
     for impl = (if pos (subseq impl/version/tag 0 pos) impl/version/tag)
@@ -122,6 +125,7 @@
     for version = (if pos2 (subseq version/tag 0 pos2) version/tag)
     for tag = (when pos2 (subseq version/tag (1+ pos2)))
     do (setf argv (rest argv))
+       (setenv *env* (format nil "~A,~A" impl/version/tag envold))
        (cond
          ;;registerd implementations like sbcl ccl-bin abcl etc
          ((setf (values _ argv) (install-impl-if-probed impl version/tag argv)))