diff --git a/rel/app/env.bat.eex b/rel/app/env.bat.eex
index bda6768692b..9a656186ee5 100644
--- a/rel/app/env.bat.eex
+++ b/rel/app/env.bat.eex
@@ -7,7 +7,7 @@ set RELEASE_MODE=interactive
 set MIX_ARCHIVES=!RELEASE_ROOT!\vendor\archives
 set MIX_REBAR3=!RELEASE_ROOT!\vendor\rebar3
 set LIVEBOOK_SHUTDOWN_ENABLED=true
-set LIVEBOOK_PORT=0
+if not defined LIVEBOOK_PORT (set LIVEBOOK_PORT=0)
 set PATH=!RELEASE_ROOT!\vendor\otp\erts-<%= @release.erts_version%>\bin;!RELEASE_ROOT!\vendor\otp\bin;!RELEASE_ROOT!\vendor\elixir\bin;!PATH!
 
 set cookie_path=!RELEASE_ROOT!\releases\COOKIE
diff --git a/rel/app/env.sh.eex b/rel/app/env.sh.eex
index 9e9b01a4389..6eaef430876 100644
--- a/rel/app/env.sh.eex
+++ b/rel/app/env.sh.eex
@@ -13,7 +13,7 @@ export RELEASE_MODE=interactive
 export MIX_ARCHIVES="${RELEASE_ROOT}/vendor/archives"
 export MIX_REBAR3="${RELEASE_ROOT}/vendor/rebar3"
 export LIVEBOOK_SHUTDOWN_ENABLED=true
-export LIVEBOOK_PORT=0
+[ -z "$LIVEBOOK_PORT" ] && export LIVEBOOK_PORT=0
 export PATH="$RELEASE_ROOT/vendor/otp/erts-<%= @release.erts_version%>/bin:$RELEASE_ROOT/vendor/otp/bin:$RELEASE_ROOT/vendor/elixir/bin:$PATH"
 
 cookie_path="${RELEASE_ROOT}/releases/COOKIE"