diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index e39bf9639b800..40537e50c1424 100644
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -58,7 +58,14 @@ ifeq ($(DEBUG), 0)
 MICROPY_ROM_TEXT_COMPRESSION ?= 1
 endif
 
-FROZEN_MANIFEST ?= modules/manifest.py
+# Enable asyncio by default and select appropriate manifest.
+MICROPY_PY_ASYNCIO ?= 1
+ifeq ($(MICROPY_PY_ASYNCIO),1)
+FROZEN_MANIFEST ?= boards/manifest.py
+else
+FROZEN_MANIFEST ?= boards/manifest_minimal.py
+endif
+CFLAGS += -DMICROPY_PY_ASYNCIO=$(MICROPY_PY_ASYNCIO)
 
 # include py core make definitions
 include ../../py/py.mk
diff --git a/ports/nrf/boards/ARDUINO_NANO_33_BLE_SENSE/manifest.py b/ports/nrf/boards/ARDUINO_NANO_33_BLE_SENSE/manifest.py
index 1e35ae8c4dd34..a196f931b3947 100644
--- a/ports/nrf/boards/ARDUINO_NANO_33_BLE_SENSE/manifest.py
+++ b/ports/nrf/boards/ARDUINO_NANO_33_BLE_SENSE/manifest.py
@@ -1,4 +1,4 @@
-include("$(PORT_DIR)/modules/manifest.py")
+include("$(PORT_DIR)/boards/manifest.py")
 require("hts221")
 require("lps22h")
 require("lsm9ds1")
diff --git a/ports/nrf/boards/MICROBIT/mpconfigboard.mk b/ports/nrf/boards/MICROBIT/mpconfigboard.mk
index 6c7e1b46b93c3..f44da7aaabe7b 100644
--- a/ports/nrf/boards/MICROBIT/mpconfigboard.mk
+++ b/ports/nrf/boards/MICROBIT/mpconfigboard.mk
@@ -10,6 +10,8 @@ else
 MICROPY_VFS_LFS2 = 1
 endif
 
+MICROPY_PY_ASYNCIO = 0
+
 LD_FILES += boards/nrf51x22_256k_16k.ld
 FLASHER = pyocd
 
diff --git a/ports/nrf/modules/manifest.py b/ports/nrf/boards/manifest.py
similarity index 100%
rename from ports/nrf/modules/manifest.py
rename to ports/nrf/boards/manifest.py
diff --git a/ports/nrf/boards/manifest_minimal.py b/ports/nrf/boards/manifest_minimal.py
new file mode 100644
index 0000000000000..674e0245271b5
--- /dev/null
+++ b/ports/nrf/boards/manifest_minimal.py
@@ -0,0 +1 @@
+module("_boot.py", base_path="$(PORT_DIR)/modules/scripts", opt=3)
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index d5cbab7310336..62e56fa1ebf13 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -97,6 +97,10 @@
 #define MICROPY_PY_BINASCII                (CORE_FEAT)
 #endif
 
+#ifndef MICROPY_PY_SELECT
+#define MICROPY_PY_SELECT                  (MICROPY_PY_ASYNCIO)
+#endif
+
 #ifndef MICROPY_PY_NRF
 #define MICROPY_PY_NRF                     (CORE_FEAT)
 #endif
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 1553c28ae4d32..1574243e8ea99 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -1887,7 +1887,7 @@ typedef time_t mp_timestamp_t;
 // implementation). This is present for compatibility but can be disabled to
 // save space.
 #ifndef MICROPY_PY_SELECT_SELECT
-#define MICROPY_PY_SELECT_SELECT (1)
+#define MICROPY_PY_SELECT_SELECT (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)
 #endif
 
 // Whether to provide the "time" module