diff --git a/MOBILE/android/ensure b/MOBILE/android/ensure
index 9a31d5c..0818fa9 100755
--- a/MOBILE/android/ensure
+++ b/MOBILE/android/ensure
@@ -6,26 +6,7 @@ __install_extra="build-tools;32.0.0 platforms;android-31"
 
 __ndk_version="23.1.7779620"
 
-GOOS=$(go env GOOS)
-case $GOOS in
-linux)
-	__sdk_dir=$HOME/Android/Sdk
-	;;
-darwin)
-	__sdk_dir=$HOME/Library/Android/sdk
-	;;
-*)
-	echo "FATAL: unsupported operating system" 1>&2
-	exit 1
-	;;
-esac
-
-ANDROID_HOME=${ANDROID_HOME:-$__sdk_dir}
-if [[ ! -d $ANDROID_HOME ]]; then
-	echo "FATAL: expected to find android SDK at $ANDROID_HOME, but found nothing" 1>&2
-	echo "HINT: run ./MOBILE/android/setup to (re)install the SDK" 1>&2
-	exit 1
-fi
+ANDROID_HOME=$(./MOBILE/android/home)
 
 __sdkmanager=$ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager
 if [[ ! -x $__sdkmanager ]]; then
diff --git a/MOBILE/android/home b/MOBILE/android/home
new file mode 100755
index 0000000..5579f60
--- /dev/null
+++ b/MOBILE/android/home
@@ -0,0 +1,30 @@
+#!/bin/bash
+
+set -euo pipefail
+
+nocheck=0
+if [[ $# -eq 1 && $1 == "--no-check" ]]; then
+	nocheck=1
+fi
+
+GOOS=$(go env GOOS)
+case $GOOS in
+linux)
+	__sdk_dir=$HOME/Android/Sdk
+	;;
+darwin)
+	__sdk_dir=$HOME/Library/Android/sdk
+	;;
+*)
+	echo "FATAL: unsupported operating system" 1>&2
+	exit 1
+	;;
+esac
+
+ANDROID_HOME=${ANDROID_HOME:-$__sdk_dir}
+if [[ $nocheck == 0 && ! -d $ANDROID_HOME ]]; then
+	echo "FATAL: expected to find android SDK at $ANDROID_HOME, but found nothing" 1>&2
+	echo "HINT: run ./MOBILE/android/setup to (re)install the SDK" 1>&2
+	exit 1
+fi
+echo $ANDROID_HOME
diff --git a/MOBILE/android/setup b/MOBILE/android/setup
index f751598..c7181f1 100755
--- a/MOBILE/android/setup
+++ b/MOBILE/android/setup
@@ -2,26 +2,25 @@
 
 set -euo pipefail
 
-GOOS=$(go env GOOS)
-case $GOOS in
-linux)
-	__sdk_dir=$HOME/Android/Sdk
-	;;
-darwin)
-	__sdk_dir=$HOME/Library/Android/sdk
-	;;
-*)
-	echo "FATAL: unsupported operating system" 1>&2
-	exit 1
-	;;
-esac
+force=0
+if [[ $# -eq 1 && $1 == "--force" ]]; then
+	force=1
+fi
 
-ANDROID_HOME=${ANDROID_HOME:-$__sdk_dir}
+ANDROID_HOME=$(./MOBILE/android/home --no-check)
 
 __clitools_version=8512546
 __clitools_file=commandlinetools-linux-${__clitools_version}_latest.zip
 __clitools_sha256=2ccbda4302db862a28ada25aa7425d99dce9462046003c1714b059b5c47970d8
 
+cmdlinetools=$ANDROID_HOME/cmdline-tools
+cmdlinetoolslatest=$cmdlinetools/latest
+
+if [[ $force == 0 && -d $cmdlinetoolslatest ]]; then
+	echo "$0: already installed... run '$0 --force' to reinstall" 1>&2
+	exit 0
+fi
+
 printf "checking for curl... "
 command -v curl || {
 	echo "not found"
@@ -39,14 +38,14 @@ command -v unzip || {
 }
 
 set -x
-rm -rf $ANDROID_HOME/cmdline-tools/latest
+rm -rf $cmdlinetoolslatest
 curl -fsSLO https://dl.google.com/android/repository/$__clitools_file
 echo "$__clitools_sha256  $__clitools_file" >__SHA256
 shasum --check __SHA256
 rm -f __SHA256
 unzip $__clitools_file
 rm $__clitools_file
-mkdir -p $ANDROID_HOME/cmdline-tools
+mkdir -p $cmdlinetools
 # See https://stackoverflow.com/a/61176718 to understand why
 # we need to reorganize the directories like this:
-mv cmdline-tools $ANDROID_HOME/cmdline-tools/latest
+mv cmdline-tools $cmdlinetoolslatest
diff --git a/Makefile b/Makefile
index f8aea09..d6063c4 100644
--- a/Makefile
+++ b/Makefile
@@ -214,7 +214,7 @@ show-config:
 #help:
 #help: * `make ./MOBILE/android/oonimkall.aar`: the AAR
 .PHONY:   ./MOBILE/android/oonimkall.aar
-./MOBILE/android/oonimkall.aar: search/for/android/sdk maybe/copypsiphon
+./MOBILE/android/oonimkall.aar: search/for/go search/for/android/sdk maybe/copypsiphon
 	./MOBILE/gomobile android ./pkg/oonimkall
 
 #help: