diff --git a/apitest/docs/api-beta-test-guide.md b/apitest/docs/api-beta-test-guide.md
index 7343410f74..73022057c1 100644
--- a/apitest/docs/api-beta-test-guide.md
+++ b/apitest/docs/api-beta-test-guide.md
@@ -43,6 +43,14 @@ $ ./gradlew clean build :apitest:installDaoSetup            # if you want to run
 
 ## Running Api Test Harness
 
+#### Warning:  Never run an API daemon and the [Bisq GUI](https://bisq.network) on the same host at the same time.
+
+The API daemon and the GUI share the same default wallet and connection ports.  Beyond inevitable failures due to
+fighting over the wallet and ports, doing so will probably corrupt your wallet.  Before starting the API daemon, make
+sure your GUI is shut down, and vice-versa.  Please back up your mainnet wallet early and often with the GUI.
+
+### Configuration And Start Command
+
 If your bitcoin-core binaries are in your system `PATH`, start bitcoind in regtest-mode, Bisq seednode and arbitration
 node daemons, plus Bob & Alice daemons in a bash terminal with the following bash command:
 ```