diff --git a/Configuration.mk b/Configuration.mk
index 141579c..3c48cd1 100644
--- a/Configuration.mk
+++ b/Configuration.mk
@@ -36,6 +36,29 @@ OPTIONS += -DBIT64
 # then run `make`. Of particular note here, sockets support
 # is disabled by default and you may wish to enable it.
 
+# The I/O devices can be enabled or disabled. Comment or
+# uncomment the corresponding ENABLED and DEVICES lines and
+# then run `make`. Of particular note here, sockets support
+# is disabled by default and you may wish to enable it.
+
+OPTIONS += -DMAKEFILE_CONFIG
+
+ENABLED ?=
+ENABLED += -DENABLE_FLOATS
+ENABLED += -DENABLE_FILES
+ENABLED += -DENABLE_UNIX
+ENABLED += -DENABLE_RNG
+ENABLED += -DENABLE_CLOCK
+ENABLED += -DENABLE_SCRIPTING
+# ENABLED += -DENABLE_SOCKETS
+ENABLED += -DENABLE_SIGNALS
+ENABLED += -DENABLE_MULTICORE
+# ENABLED += -DENABLE_FFI
+ENABLED += -DENABLE_ERROR
+ENABLED += -DENABLE_UNSIGNED
+ENABLED += -DENABLE_MALLOC
+ENABLED += -DENABLE_BLOCKS
+
 DEVICES ?=
 DEVICES += interface/ll.retro
 DEVICES += interface/dedup.retro
diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index 0be1c49..e0d7e93 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -41,5 +41,8 @@
   hang on startup
 - added an initial man page for retro-compiler(1)
 - added new example showing decompression of ulz files
+- configuration of devices can now be done in either config.h
+  or (by default) Configuration.mk
+- build instructions for enabling/disabling devices updated
 
 ================================================================
diff --git a/doc/RETRO-Book.md b/doc/RETRO-Book.md
index ffc340e..e3010a6 100644
--- a/doc/RETRO-Book.md
+++ b/doc/RETRO-Book.md
@@ -302,8 +302,8 @@ be using this).
 ## I/O Devices
 
 Many of the I/O devices are optional. The most common ones are
-enabled by default in the Makefile. Look near the end of the top
-section for lines starting with `ENABLED`:
+enabled by default in the Configuration.mk. Look for the lines
+starting with `ENABLED`:
 
     ENABLED ?=
     ENABLED += -DENABLE_FLOATS
diff --git a/doc/book/building/advanced b/doc/book/building/advanced
index 098a54e..deb2874 100644
--- a/doc/book/building/advanced
+++ b/doc/book/building/advanced
@@ -10,8 +10,8 @@ be using this).
 ## I/O Devices
 
 Many of the I/O devices are optional. The most common ones are
-enabled by default in the Makefile. Look near the end of the top
-section for lines starting with `ENABLED`:
+enabled by default in the Configuration.mk. Look for the lines
+starting with `ENABLED`:
 
     ENABLED ?=
     ENABLED += -DENABLE_FLOATS
diff --git a/vm/nga-c/config.h b/vm/nga-c/config.h
index 24ec391..07ca931 100644
--- a/vm/nga-c/config.h
+++ b/vm/nga-c/config.h
@@ -11,6 +11,7 @@
 
 **************************************************************/
 
+#ifndef MAKEFILE_CONFIG
 #define ENABLE_FLOATS
 #define ENABLE_FILES
 #define ENABLE_UNIX
@@ -25,6 +26,7 @@
 #define ENABLE_UNSIGNED
 #define ENABLE_MALLOC
 #define ENABLE_BLOCKS
+#endif
 
 #ifdef ENABLE_MULTICORE
 #define CORES 8