diff --git a/clamav.spec b/clamav.spec
index 900c2f7..54803c5 100644
--- a/clamav.spec
+++ b/clamav.spec
@@ -540,7 +540,7 @@ test -e %freshclamlog || {
 %triggerin milter -- clamav-scanner
 # Add the milteruser to the scanuser group; this is required when
 # milter and clamd communicate through local sockets
-/usr/sbin/usermod -a -G %scanuser %milteruser &>/dev/null || :
+/usr/sbin/groupmems -g %scanuser -a %milteruser &>/dev/null || :
 
 %pre milter
 %__fe_groupadd 5 -r %milteruser &>/dev/null || :
@@ -705,6 +705,10 @@ test "$1" != "0" || /sbin/initctl -q stop clamav-milter || :
 
 
 %changelog
+* Wed Aug 11 2010 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
+- use 'groupmems', not 'usermod' to add a user to a group because
+  'usermod' does not work when user does not exist in local /etc/passwd
+
 * Tue Jun  1 2010 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de> - 0.96.1-1400
 - updated to 0.96.1
 - applied upstream patch which allows to disable JIT compiler (#573191)