diff --git a/app/build.gradle b/app/build.gradle
index abf798791bb77733a3cd406e0b261cd8023de5ee..6b77a66e0b50c5bfa63ede76edb2be3e162aa53d 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -23,8 +23,8 @@ android {
     defaultConfig {
         applicationId "foundation.e.accountmanager"
 
-        versionCode 403090005
-        versionName '4.3.10'
+        versionCode 403090006
+        versionName '4.3.9-6'
 
         buildConfigField "long", "buildTime", System.currentTimeMillis() + "L"
 
@@ -84,10 +84,17 @@ android {
             keyAlias System.getenv("ANDROID_KEY_ALIAS")
             keyPassword System.getenv("ANDROID_KEY_PASSWORD")
         }
+        debug {
+            storeFile file("keystore/platform.jks")
+            storePassword "platform"
+            keyAlias "platform"
+            keyPassword "platform"
+        }
     }
 
     buildTypes {
         debug {
+            signingConfig = signingConfigs.debug
             buildConfigField "String", "EMAIL_KEY", "\"invalid\""
         }
 
diff --git a/app/keystore/platform.jks b/app/keystore/platform.jks
new file mode 100644
index 0000000000000000000000000000000000000000..b778840542e79c048bcf570aa960243eeb9b9d53
Binary files /dev/null and b/app/keystore/platform.jks differ
diff --git a/app/src/main/kotlin/at/bitfire/davdroid/settings/AccountSettings.kt b/app/src/main/kotlin/at/bitfire/davdroid/settings/AccountSettings.kt
index a3fb1d3ad071f2e31b44392da3f10cb37644afbc..abbb5855ee3323f29a50e8f5e8db953477e002e6 100644
--- a/app/src/main/kotlin/at/bitfire/davdroid/settings/AccountSettings.kt
+++ b/app/src/main/kotlin/at/bitfire/davdroid/settings/AccountSettings.kt
@@ -201,18 +201,17 @@ class AccountSettings(
         }
 
         private fun addEmailToBundle(bundle: Bundle, email: String?, userName: String?) {
-            if (email != null) {
+            if (!email.isNullOrEmpty() && email != "null") {
                 bundle.putString(KEY_EMAIL_ADDRESS, email)
                 return
             }
 
             userName?.let {
-                if (it.contains("@")) {
+                if (it != "null" && it.contains("@")) {
                     bundle.putString(KEY_EMAIL_ADDRESS, it)
                 }
             }
         }
-
     }