diff --git a/.gitignore b/.gitignore
index 0741eb7..26672fb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1 @@
-ccache-2.4.tar.gz
+/ccache-2.4.tar.gz
diff --git a/ccache.csh.in b/ccache.csh.in
index 846fead..4edbb51 100644
--- a/ccache.csh.in
+++ b/ccache.csh.in
@@ -1,16 +1,26 @@
-# Use ccache by default.  Users who don't want that can set the CCACHE_DISABLE
-# environment variable in their personal profile.
+# Use ccache by default.  Users who don't want that can setenv the
+# CCACHE_DISABLE environment variable in their personal profile.
 
 if ( "$path" !~ *@LIBDIR@/ccache* ) then
     set path = ( @LIBDIR@/ccache $path )
 endif
 
-# If @CACHEDIR@ is writable, use a shared cache there.  Users who don't
-# want that even if they have that write permission can set the CCACHE_DIR
-# and unset the CCACHE_UMASK environment variables in their personal profile.
+# If @CACHEDIR@ is writable, use a shared cache there, except for root.
+# Users who don't want that even if they have the write permission can setenv
+# the CCACHE_DIR environment variable to another location and possibly unsetenv
+# the CCACHE_UMASK environment variable in their personal profile.
 
-if ( ! $?CCACHE_DIR && -w @CACHEDIR@ && -d @CACHEDIR@ ) then
-    setenv CCACHE_DIR @CACHEDIR@
-    setenv CCACHE_UMASK 002
-    unsetenv CCACHE_HARDLINK
+if ( $?CCACHE_DIR ) then
+    if ( ! -w "$CCACHE_DIR" ) then
+        # Reset broken settings maybe inherited when switching users (#651023).
+        unsetenv CCACHE_DIR
+        unsetenv CCACHE_UMASK
+    endif
+else if ( $uid != 0 ) then
+    if ( -w @CACHEDIR@ && -d @CACHEDIR@ ) then
+        # Set up the shared cache.
+        setenv CCACHE_DIR @CACHEDIR@
+        setenv CCACHE_UMASK 002
+        unsetenv CCACHE_HARDLINK
+    endif
 endif
diff --git a/ccache.sh.in b/ccache.sh.in
index c751a60..0ce4d64 100644
--- a/ccache.sh.in
+++ b/ccache.sh.in
@@ -1,17 +1,27 @@
 # Use ccache by default.  Users who don't want that can set the CCACHE_DISABLE
 # environment variable in their personal profile.
 
-case ":$PATH:" in
+case ":${PATH:-}:" in
     *:@LIBDIR@/ccache:*) ;;
-    *) PATH="@LIBDIR@/ccache:$PATH" ;;
+    *) PATH="@LIBDIR@/ccache${PATH:+:$PATH}" ;;
 esac
 
-# If @CACHEDIR@ is writable, use a shared cache there.  Users who don't
-# want that even if they have that write permission can set the CCACHE_DIR
-# and unset the CCACHE_UMASK environment variables in their personal profile.
+# If @CACHEDIR@ is writable, use a shared cache there, except for root.
+# Users who don't want that even if they have the write permission can set
+# the CCACHE_DIR environment variable to another location and possibly unset
+# the CCACHE_UMASK environment variables in their personal profile.
 
-if [ -z "$CCACHE_DIR" ] && [ -w @CACHEDIR@ ] && [ -d @CACHEDIR@ ] ; then
-    export CCACHE_DIR=@CACHEDIR@
-    export CCACHE_UMASK=002
-    unset CCACHE_HARDLINK
+if [ -n "${CCACHE_DIR:-}" ] ; then
+    if [ ! -w "$CCACHE_DIR" ] ; then
+        # Reset broken settings maybe inherited when switching users (#651023).
+        unset CCACHE_DIR
+        unset CCACHE_UMASK
+    fi
+elif [ "${EUID:-}" != 0 ] ; then
+    if [ -w @CACHEDIR@ ] && [ -d @CACHEDIR@ ] ; then
+        # Set up the shared cache.
+        export CCACHE_DIR=@CACHEDIR@
+        export CCACHE_UMASK=002
+        unset CCACHE_HARDLINK
+    fi
 fi
diff --git a/ccache.spec b/ccache.spec
index 39131b9..e1cbaf9 100644
--- a/ccache.spec
+++ b/ccache.spec
@@ -6,7 +6,7 @@
 
 Name:           ccache
 Version:        2.4
-Release:        18%{?dist}
+Release:        19%{?dist}
 Summary:        C/C++ compiler cache
 
 Group:          Development/Tools
@@ -102,6 +102,10 @@ done
 
 
 %changelog
+* Sat Apr  2 2011 Ville Skyttä <ville.skytta@iki.fi> - 2.4-19
+- Reset non-working cache dir related env settings on user switch (#651023).
+- Make sh profile script "nounset" clean.
+
 * Fri Jun  4 2010 Ville Skyttä <ville.skytta@iki.fi> - 2.4-18
 - Don't use "pathmunge" in the profile.d sh script to work around #548960.