diff --git a/x11-misc/gromit-mpx/files/gromit-mpx-1.4.3-fwd-declare-app_parse_args.patch b/x11-misc/gromit-mpx/files/gromit-mpx-1.4.3-fwd-declare-app_parse_args.patch
new file mode 100644
index 0000000000..90367cfb48
--- /dev/null
+++ b/x11-misc/gromit-mpx/files/gromit-mpx-1.4.3-fwd-declare-app_parse_args.patch
@@ -0,0 +1,16 @@
+Fixes compilation with -Werror,-Wimplicit-function-declaration.
+
+Bug: https://bugs.gentoo.org/888149
+Bug: https://github.com/bk138/gromit-mpx/pull/173
+
+--- gromit-mpx-1.4.3/src/gromit-mpx.c	2022-09-25 14:43:43.000000000 +0200
++++ gromit-mpx-1.4.3/src/gromit-mpx.c	2022-12-24 18:32:23.629233288 +0100
+@@ -696,7 +696,7 @@
+ }
+ 
+ 
+-
++int app_parse_args (int argc, char **argv, GromitData *data);
+ 
+ 
+ void setup_main_app (GromitData *data, int argc, char ** argv)
diff --git a/x11-misc/gromit-mpx/gromit-mpx-1.4.3.ebuild b/x11-misc/gromit-mpx/gromit-mpx-1.4.3.ebuild
index 95600ede05..1d64637ab5 100644
--- a/x11-misc/gromit-mpx/gromit-mpx-1.4.3.ebuild
+++ b/x11-misc/gromit-mpx/gromit-mpx-1.4.3.ebuild
@@ -27,6 +27,10 @@ RDEPEND="
 "
 DEPEND="${RDEPEND}"
 
+PATCHES=(
+	"${FILESDIR}"/${PN}-1.4.3-fwd-declare-app_parse_args.patch
+)
+
 src_prepare () {
 	cmake_src_prepare
 }