diff --git a/ghc-rpm-macros.changes b/ghc-rpm-macros.changes
index 8a62021..3ba4e7e 100644
--- a/ghc-rpm-macros.changes
+++ b/ghc-rpm-macros.changes
@@ -1,3 +1,20 @@
+-------------------------------------------------------------------
+Tue Oct 24 14:39:05 UTC 2023 - Peter Simons <psimons@suse.com>
+
+- Apply "reproducible-builds.patch", which makes GHC output
+  deterministic by disabling multi-threaded compilation. Adding
+
+    Macros:
+      # Enable multi-threaded builds in this project. This makes our
+      # build products non-deterministic, e.g. not reproducible, but
+      # we don't need them to be and would rather have fast results.
+      %ghc_smp_mflags %{?_smp_mflags}
+    :Macros
+
+  to an OBS project configuration re-enables multi-threaded builds,
+  which might be useful for development projects that don't deliver
+  binaries.
+
 -------------------------------------------------------------------
 Sun Aug  6 14:34:29 UTC 2023 - Ondřej Súkup <mimi.vx@gmail.com>
 
@@ -24,7 +41,7 @@ Thu Mar 16 18:26:11 UTC 2023 - Ondřej Súkup <mimi.vx@gmail.com>
 -------------------------------------------------------------------
 Mon Nov  1 05:59:41 UTC 2021 - Ondřej Súkup <mimi.vx@gmail.com>
 
-- fix build, remove white space 
+- fix build, remove white space
 
 -------------------------------------------------------------------
 Mon May 10 10:37:06 UTC 2021 - Ondřej Súkup <mimi.vx@gmail.com>
diff --git a/ghc-rpm-macros.spec b/ghc-rpm-macros.spec
index 9b0e5fc..b4b6f46 100644
--- a/ghc-rpm-macros.spec
+++ b/ghc-rpm-macros.spec
@@ -26,6 +26,7 @@ Group:          Development/Libraries/Other
 URL:            https://fedoraproject.org/wiki/Haskell_SIG
 # source gets updated with osc service dr
 Source0:        %{name}-%{version}.tar.xz
+Patch1:         https://github.com/opensuse-haskell/ghc-rpm-macros/pull/1.patch#/reproducible-builds.patch
 BuildRequires:  xz
 Requires:       rpm
 Requires:       chrpath
@@ -49,7 +50,7 @@ Extra macros used for subpackaging of Haskell libraries,
 for example in ghc and haskell-platform.
 
 %prep
-%setup -q
+%autosetup -p1
 
 %build
 echo no build stage needed
diff --git a/reproducible-builds.patch b/reproducible-builds.patch
new file mode 100644
index 0000000..17a50aa
--- /dev/null
+++ b/reproducible-builds.patch
@@ -0,0 +1,25 @@
+From fc753c7f752ea77650ca708104acc384f025dd54 Mon Sep 17 00:00:00 2001
+From: "Bernhard M. Wiedemann" <bwiedemann@suse.de>
+Date: Sat, 15 Apr 2023 07:09:01 +0200
+Subject: [PATCH] Compile with only 1 thread
+
+but give an option to do fast non-deterministic builds
+
+parallel compile causes assignment of random symbol names
+so we build single-threaded, which is slower, but gives reproducible results
+---
+ macros.ghc-suse | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/macros.ghc-suse b/macros.ghc-suse
+index 3fe39a0..61a154a 100644
+--- a/macros.ghc-suse
++++ b/macros.ghc-suse
+@@ -29,4 +29,6 @@ mkdir -p %{buildroot}/usr/src/debug
+ %with_ghc_prof 1
+ 
+ # %%{?_smp_ncpus_max:--jobs=%%{?_smp_ncpus_max}}
+-%ghc_smp_mflags %{?_smp_mflags}
++# parallel compile causes assignment of random symbol names
++# so for distribution releases we build single-threaded, which is slower, but gives reproducible results
++# for devel project set ghc_smp_flags in Macros