diff --git a/dev-libs/olm/files/olm-3.2.16-cmake4.patch b/dev-libs/olm/files/olm-3.2.16-cmake4.patch
new file mode 100644
index 0000000000000..a480d8d2c552c
--- /dev/null
+++ b/dev-libs/olm/files/olm-3.2.16-cmake4.patch
@@ -0,0 +1,23 @@
+From 6447282221084f46a7d39cf5a71ebd063a2302df Mon Sep 17 00:00:00 2001
+From: Andreas Sturmlechner <asturm@gentoo.org>
+Date: Sun, 5 Oct 2025 16:21:57 +0200
+Subject: [PATCH] Raise cmake_minimum_required to 3.31 to fix build w/ cmake-4
+
+Signed-off-by: Andreas Sturmlechner <asturm@gentoo.org>
+---
+ CMakeLists.txt | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 951965f..24ca631 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,4 +1,4 @@
+-cmake_minimum_required(VERSION 3.4)
++cmake_minimum_required(VERSION 3.31)
+ 
+ project(olm VERSION 3.2.16 LANGUAGES CXX C)
+ 
+-- 
+2.51.0
+
diff --git a/dev-libs/olm/olm-3.2.16-r1.ebuild b/dev-libs/olm/olm-3.2.16-r1.ebuild
index d00872b902ccd..c14640533cfdc 100644
--- a/dev-libs/olm/olm-3.2.16-r1.ebuild
+++ b/dev-libs/olm/olm-3.2.16-r1.ebuild
@@ -15,11 +15,19 @@ KEYWORDS="amd64 arm64 ~ppc64 x86"
 IUSE="test"
 RESTRICT="!test? ( test )"
 
+BDEPEND=">=dev-build/cmake-3.31"
+
 PATCHES=(
 	"${FILESDIR}/${P}-cmake.patch" # TODO: upstream
+	"${FILESDIR}/${P}-cmake4.patch" # bug 955895
 	"${FILESDIR}/${P}-clang-19-const.patch"
 )
 
+src_prepare() {
+	rm -rv lib/doctest || die # unused bundled stuff using <CMake-3.5
+	cmake_src_prepare
+}
+
 src_configure() {
 	local mycmakeargs=(
 		-DBUILD_TESTING=$(usex test)