diff --git a/README.md b/README.md
index da638f4..43b23c6 100644
--- a/README.md
+++ b/README.md
@@ -35,11 +35,32 @@ build_vars:
 Note: OTA will not work on these devices, for lack of flash space for the
 alternate boot partition.
 
+When updating these, ensure you have a copy of the timespec files:
+
+```
+mos get timespec.chan0
+mos get timespec.chan1
+mos get timespec.chan2
+mos get timespec.chan3
+```
+
+After flashing, but them back:
+
+```
+mos put timespec.chan0
+mos put timespec.chan1
+mos put timespec.chan2
+mos put timespec.chan3
+```
+
 ### Using Sonoff-4CH
 
+Don't forget to copy the timespec files!
+
 Sonoff 4CH uses a bunch of GPIO pins for the LEDs and pushbuttons, and as such
 has no space for sensors.
 
 ```
 mos config-set app.config=sonoff-4ch.json sensors.dht_gpio=""
 ```
+
diff --git a/mos.yml b/mos.yml
index 48361a0..092543a 100644
--- a/mos.yml
+++ b/mos.yml
@@ -44,8 +44,8 @@ config_schema:
   - ["debug.log_udp_addr", "192.168.1.20:1234"]
 
 
-build_vars:
-  FLASH_SIZE: 1048576
+#build_vars:
+#  FLASH_SIZE: 1048576
 
 # List of libraries used by this app, in order of initialisation
 libs: