diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index bf3d2b8..22f80bb 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -67,6 +67,8 @@
     xtea.c
 )
 
+# For files generated by the parent project (Mbed TLS) when building Mbed
+# Crypto as a submodule, ensure that the parent project instance is used.
 if(USE_CRYPTO_SUBMODULE)
 set(src_crypto
     ${src_crypto}