diff --git a/config/thisroot.csh b/config/thisroot.csh
index 08193bce3ecd0bbf5fdd7a0744925b2f1e657d6e..f61942b2e3ec0012593a794f32cc147556e3bdb9 100644
--- a/config/thisroot.csh
+++ b/config/thisroot.csh
@@ -59,64 +59,64 @@ setenv ROOTSYS "`(cd ${thisroot}/..;pwd)`"
 
 if ($?old_rootsys) then
    setenv PATH `echo $PATH | sed -e "s;:$old_rootsys/bin:;:;g" \
-                                 -e "s;:$old_rootsys/bin;;g"   \
-                                 -e "s;$old_rootsys/bin:;;g"   \
-                                 -e "s;$old_rootsys/bin;;g"`
+                                 -e "s;:$old_rootsys/bin$$;;g"   \
+                                 -e "s;^$old_rootsys/bin:;;g"   \
+                                 -e "s;^$old_rootsys/bin$$;;g"`
    if ($?LD_LIBRARY_PATH) then
       setenv LD_LIBRARY_PATH `echo $LD_LIBRARY_PATH | \
                              sed -e "s;:$old_rootsys/lib:;:;g" \
-                                 -e "s;:$old_rootsys/lib;;g"   \
-                                 -e "s;$old_rootsys/lib:;;g"   \
-                                 -e "s;$old_rootsys/lib;;g"`
+                                 -e "s;:$old_rootsys/lib$$;;g"   \
+                                 -e "s;^$old_rootsys/lib:;;g"   \
+                                 -e "s;^$old_rootsys/lib$$;;g"`
    endif
    if ($?DYLD_LIBRARY_PATH) then
       setenv DYLD_LIBRARY_PATH `echo $DYLD_LIBRARY_PATH | \
                              sed -e "s;:$old_rootsys/lib:;:;g" \
-                                 -e "s;:$old_rootsys/lib;;g"   \
-                                 -e "s;$old_rootsys/lib:;;g"   \
-                                 -e "s;$old_rootsys/lib;;g"`
+                                 -e "s;:$old_rootsys/lib$$;;g"   \
+                                 -e "s;^$old_rootsys/lib:;;g"   \
+                                 -e "s;^$old_rootsys/lib$$;;g"`
    endif
    if ($?SHLIB_PATH) then
       setenv SHLIB_PATH `echo $SHLIB_PATH | \
                              sed -e "s;:$old_rootsys/lib:;:;g" \
-                                 -e "s;:$old_rootsys/lib;;g"   \
-                                 -e "s;$old_rootsys/lib:;;g"   \
-                                 -e "s;$old_rootsys/lib;;g"`
+                                 -e "s;:$old_rootsys/lib$$;;g"   \
+                                 -e "s;^$old_rootsys/lib:;;g"   \
+                                 -e "s;^$old_rootsys/lib$$;;g"`
    endif
    if ($?LIBPATH) then
       setenv LIBPATH `echo $LIBPATH | \
                              sed -e "s;:$old_rootsys/lib:;:;g" \
-                                 -e "s;:$old_rootsys/lib;;g"   \
-                                 -e "s;$old_rootsys/lib:;;g"   \
-                                 -e "s;$old_rootsys/lib;;g"`
+                                 -e "s;:$old_rootsys/lib$$;;g"   \
+                                 -e "s;^$old_rootsys/lib:;;g"   \
+                                 -e "s;^$old_rootsys/lib$$;;g"`
    endif
    if ($?PYTHONPATH) then
       setenv PYTHONPATH `echo $PYTHONPATH | \
                              sed -e "s;:$old_rootsys/lib:;:;g" \
-                                 -e "s;:$old_rootsys/lib;;g"   \
-                                 -e "s;$old_rootsys/lib:;;g"   \
-                                 -e "s;$old_rootsys/lib;;g"`
+                                 -e "s;:$old_rootsys/lib$$;;g"   \
+                                 -e "s;^$old_rootsys/lib:;;g"   \
+                                 -e "s;^$old_rootsys/lib$$;;g"`
    endif
    if ($?MANPATH) then
       setenv MANPATH `echo $MANPATH | \
                              sed -e "s;:$old_rootsys/man:;:;g" \
-                                 -e "s;:$old_rootsys/man;;g"   \
-                                 -e "s;$old_rootsys/man:;;g"   \
-                                 -e "s;$old_rootsys/man;;g"`
+                                 -e "s;:$old_rootsys/man$$;;g"   \
+                                 -e "s;^$old_rootsys/man:;;g"   \
+                                 -e "s;^$old_rootsys/man$$;;g"`
    endif
    if ($?CMAKE_PREFIX_PATH) then
       setenv CMAKE_PREFIX_PATH `echo $CMAKE_PREFIX_PATH | \
                              sed -e "s;:${old_rootsys}:;:;g" \
-                                 -e "s;:${old_rootsys};;g"   \
-                                 -e "s;${old_rootsys}:;;g"   \
-                                 -e "s;${old_rootsys};;g"`
+                                 -e "s;:${old_rootsys}$$;;g"   \
+                                 -e "s;^${old_rootsys}:;;g"   \
+                                 -e "s;^${old_rootsys}$$;;g"`
    endif
    if ($?JUPYTER_PATH) then
       setenv JUPYTER_PATH `echo $JUPYTER_PATH | \
                              sed -e "s;:$old_rootsys/etc/notebook:;:;g" \
-                                 -e "s;:$old_rootsys/etc/notebook;;g"   \
-                                 -e "s;$old_rootsys/etc/notebook:;;g"   \
-                                 -e "s;$old_rootsys/etc/notebook;;g"`
+                                 -e "s;:$old_rootsys/etc/notebook$$;;g"   \
+                                 -e "s;^$old_rootsys/etc/notebook:;;g"   \
+                                 -e "s;^$old_rootsys/etc/notebook$$;;g"`
    endif
 
 endif
diff --git a/config/thisroot.sh b/config/thisroot.sh
index cb3f54149ca74f4b0eebdb7a1dc6c3cced4708dd..7cb3e53277d2c64d6c539ddf59becb62b2110e69 100644
--- a/config/thisroot.sh
+++ b/config/thisroot.sh
@@ -19,9 +19,9 @@ drop_from_path()
    drop=$2
 
    newpath=`echo $p | sed -e "s;:${drop}:;:;g" \
-                          -e "s;:${drop};;g"   \
-                          -e "s;${drop}:;;g"   \
-                          -e "s;${drop};;g"`
+                          -e "s;:${drop}\$;;g"   \
+                          -e "s;^${drop}:;;g"   \
+                          -e "s;^${drop}\$;;g"`
 }
 
 if [ -n "${ROOTSYS}" ] ; then