diff --git a/CMakeLists.txt b/CMakeLists.txt
index f09ae76..9b9eaf1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.5)
-project(libxeddsa VERSION 2.0.0)
+project(libxeddsa VERSION 2.0.0 LANGUAGES C)
 
 include(CTest)
 
diff --git a/ref10/CMakeLists.txt b/ref10/CMakeLists.txt
index 32e068c..cc3217c 100644
--- a/ref10/CMakeLists.txt
+++ b/ref10/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.5)
-project(ref10)
+project(ref10 LANGUAGES C)
 
 include(CTest)