diff --git a/12to11-1.0.0-wayland-1.21-compat.patch b/12to11-1.0.0-wayland-1.21-compat.patch
new file mode 100644
index 0000000..804f462
--- /dev/null
+++ b/12to11-1.0.0-wayland-1.21-compat.patch
@@ -0,0 +1,17 @@
+diff --git a/src/subsurface.c b/src/subsurface.c
+--- a/src/subsurface.c
++++ b/src/subsurface.c
+@@ -23,6 +23,13 @@
+ 
+ #include "compositor.h"
+ 
++#include <wayland-version.h>
++
++/* wayland < 1.22 lacks wl_subcompositor's bad_parent error.  */
++#if WAYLAND_VERSION_MAJOR == 1 && WAYLAND_VERSION_MINOR < 22
++#define WL_SUBCOMPOSITOR_ERROR_BAD_PARENT 1
++#endif
++
+ enum
+   {
+     PendingPosition	 = 1,
diff --git a/12to11.spec b/12to11.spec
index 3288621..2a6bd61 100644
--- a/12to11.spec
+++ b/12to11.spec
@@ -17,13 +17,19 @@
 
 Name:           12to11
 Version:        1.0.0
-Release:        2%{?dist}
+Release:        3%{?dist}
 Summary:        Wayland to X11 protocol translator
 
 License:        GPL-3.0-only
 URL:            https://github.com/fish4terrisa-MSDSM/12to11
 Source0:        %{url}/archive/refs/tags/v%{version}/%{name}-%{version}.tar.gz
 
+# EL9 ships wayland 1.21, which lacks WL_SUBCOMPOSITOR_ERROR_BAD_PARENT
+# (added in wayland 1.22).  Only needed on EL9.
+%if 0%{?rhel} == 9
+Patch0:         12to11-1.0.0-wayland-1.21-compat.patch
+%endif
+
 # Build dependencies
 BuildRequires:  make
 BuildRequires:  gcc
@@ -74,7 +80,7 @@ fish4terrisa-MSDSM; the original SourceForge project has been
 unmaintained since 2022.
 
 %prep
-%autosetup
+%autosetup -p1
 
 %build
 # Export the RPM build flags: the Makefile uses CFLAGS ?= / LDFLAGS +=
@@ -95,6 +101,10 @@ export LDFLAGS="%{?build_ldflags}"
 %{_mandir}/man1/12to11.1*
 
 %changelog
+* Tue Sep 15 2026 Anders da Silva Rytter Hansen <andersrh@users.noreply.github.com> - 1.0.0-3
+- Add patch defining WL_SUBCOMPOSITOR_ERROR_BAD_PARENT for wayland < 1.22;
+  applied only on EL9 (which ships wayland 1.21).
+
 * Tue Sep 15 2026 Anders da Silva Rytter Hansen <andersrh@users.noreply.github.com> - 1.0.0-2
 - Require libXi-devel >= 1.8 for the XI 2.4 gesture event types; on EL9
   the newer libXi is supplied by this COPR project (EL9 ships 1.7.10).