diff --git a/Makefile.inc b/Makefile.inc
index 94c57a3..0079c03 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -1,10 +1,36 @@
-LC_SRCS+=	aead.c aead_chacha20_poly1305.c
-LC_SRCS+=	auth.c auth_hmac.c auth_poly1305.c
-LC_SRCS+=	cipher.c cipher_chacha20.c
-LC_SRCS+=	hash.c hash_sha224_sha256.c hash_sha384_sha512.c
-LC_SRCS+=	impl_chacha20.c impl_poly1305.c impl_sha256.c impl_sha512.c
-LC_SRCS+=	kdf.c kdf_hkdf.c
-LC_SRCS+=	ct.c util.c
+# Constant time.
+LC_SRCS+=	ct.c
+
+# Utilities.
+LC_SRCS+=	util.c
+
+# AEAD.
+LC_SRCS+=	aead.c
+LC_SRCS+=	aead_chacha20_poly1305.c
+
+# Authentication.
+LC_SRCS+=	auth.c
+LC_SRCS+=	auth_hmac.c
+LC_SRCS+=	auth_poly1305.c
+
+# Ciphers.
+LC_SRCS+=	cipher.c
+LC_SRCS+=	cipher_chacha20.c
+
+# Hashes.
+LC_SRCS+=	hash.c
+LC_SRCS+=	hash_sha224_sha256.c
+LC_SRCS+=	hash_sha384_sha512.c
+
+# Key-derivation functions.
+LC_SRCS+=	kdf.c
+LC_SRCS+=	kdf_hkdf.c
+
+# Implementations.
+LC_SRCS+=	impl_chacha20.c
+LC_SRCS+=	impl_poly1305.c
+LC_SRCS+=	impl_sha256.c
+LC_SRCS+=	impl_sha512.c
 
 WARNINGS=	Yes