diff --git a/atdna/atdnaHelpers.cmake b/atdna/atdnaHelpers.cmake
index 0b27396..861b63f 100644
--- a/atdna/atdnaHelpers.cmake
+++ b/atdna/atdnaHelpers.cmake
@@ -3,6 +3,9 @@
 # across all dependencies.
 #
 
+# CMake 3.20: Transform add_custom_command DEPFILE for Ninja
+cmake_policy(SET CMP0116 NEW)
+
 function(_atdna_gather_include_directories_impl target_name)
   get_target_property(target_dependencies ${target_name} INTERFACE_LINK_LIBRARIES)
   foreach(dep ${target_dependencies})