diff --git a/CMakeLists.txt b/CMakeLists.txt
index 76516be..78af77c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,12 +1,12 @@
 # debian stable (currently bullseye)
-cmake_minimum_required(VERSION 3.18)
+cmake_minimum_required(VERSION 3.20)
 
 project(
   tug
   VERSION 0.4
   LANGUAGES CXX)
 
-find_package(Eigen3 3.4 REQUIRED NO_MODULE)
+find_package(Eigen3 3.4...5 REQUIRED NO_MODULE)
 find_package(OpenMP)
 
 include(GNUInstallDirs)
diff --git a/README.md b/README.md
index 54213ac..089cd1a 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ grid with constant alpha for all grid cells can be solved reliably.
 # Requirements
 
 - C++17 compliant compiler
-- [CMake](https://cmake.org/) >= 3.18
+- [CMake](https://cmake.org/) >= 3.20
 - [Eigen](https://eigen.tuxfamily.org/) >= 3.4.0
 
 # Getting started