diff --git a/mobile/android/confvars.sh b/mobile/android/confvars.sh
index 5845ac249e6f..32274c916374 100755
--- a/mobile/android/confvars.sh
+++ b/mobile/android/confvars.sh
@@ -49,3 +49,4 @@ MOZ_ANDROID_OMTC=1
 MOZ_EXTENSION_MANAGER=1
 MOZ_APP_STATIC_INI=1
 
+MOZ_PER_WINDOW_PRIVATE_BROWSING=1