diff --git a/ChangeLog b/ChangeLog
index 32f2dec0..b19adfbe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -11,6 +11,7 @@ ver. 1.1.2-dev-1 (20??/??/??) - development nightly edition
 -----------
 
 ### Fixes
+* `filter.d/postfix.conf` - monitor all Postfix instances in `system-postfix.slice` with the systemd backend (gh-4008)
 * `filter.d/nginx-botsearch.conf` - error-log regex extended with support of journal format (gh-3732)
 * `filter.d/apache-noscript.conf` - match a request for the `cgi-bin` directory itself (no script name after it),
   the `cgi-bin` alternative required a following path segment so `/cgi-bin/` and `/cgi-bin` were not matched (gh-4217)
diff --git a/THANKS b/THANKS
index 7c008c2c..24417e28 100644
--- a/THANKS
+++ b/THANKS
@@ -95,6 +95,7 @@ Michael C. Haller
 Michael Hanselmann
 Mika (mkl)
 Nick Munger
+omrzk
 onorua
 Orion Poplawski
 Pablo Rodriguez Fernandez
diff --git a/config/filter.d/postfix.conf b/config/filter.d/postfix.conf
index 0c7f34b0..b24d49b0 100644
--- a/config/filter.d/postfix.conf
+++ b/config/filter.d/postfix.conf
@@ -90,6 +90,6 @@ ignoreregex =
 
 [Init]
 
-journalmatch = _SYSTEMD_UNIT=postfix.service _SYSTEMD_UNIT=postfix@-.service
+journalmatch = _SYSTEMD_UNIT=postfix.service _SYSTEMD_UNIT=postfix@-.service + _SYSTEMD_SLICE=system-postfix.slice
 
 # Author: Cyril Jaquier