diff --git a/app/src/main/java/com/orgzly/android/repos/WebdavRepo.kt b/app/src/main/java/com/orgzly/android/repos/WebdavRepo.kt
index d21fd0ff2..cd85d9df7 100644
--- a/app/src/main/java/com/orgzly/android/repos/WebdavRepo.kt
+++ b/app/src/main/java/com/orgzly/android/repos/WebdavRepo.kt
@@ -1,18 +1,23 @@
 package com.orgzly.android.repos
 
 import android.net.Uri
+import android.os.Build
 import com.orgzly.android.BookName
+import com.orgzly.android.util.TLSSocketFactory
 import com.orgzly.android.util.UriUtils
 import com.thegrizzlylabs.sardineandroid.DavResource
 import com.thegrizzlylabs.sardineandroid.impl.OkHttpSardine
+import okhttp3.CipherSuite
+import okhttp3.ConnectionSpec
 import okhttp3.OkHttpClient
+import okhttp3.TlsVersion
 import okio.Buffer
 import java.io.File
 import java.io.FileOutputStream
 import java.io.InputStream
 import java.security.KeyStore
 import java.security.cert.CertificateFactory
-import java.util.*
+import java.util.Arrays
 import javax.net.ssl.*
 
 
@@ -29,57 +34,55 @@ class WebdavRepo(
     }
 
     private fun client(certificates: String?): OkHttpSardine {
-        return if (certificates.isNullOrEmpty()) {
-            OkHttpSardine()
+        return OkHttpSardine(okHttpClient(certificates))
+    }
+
+    private fun okHttpClient(certificates: String?): OkHttpClient {
+        val trustManager = x509TrustManager(certificates)
+        val builder = OkHttpClient.Builder()
+        if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT < 22) {
+            builder.sslSocketFactory(TLSSocketFactory(trustManager), trustManager)
+                .connectionSpecs(arrayListOf(
+                    ConnectionSpec.Builder(ConnectionSpec.MODERN_TLS)
+                        .allEnabledTlsVersions()
+                        .allEnabledCipherSuites()
+                        .build(),
+                    ConnectionSpec.COMPATIBLE_TLS,
+                    ConnectionSpec.CLEARTEXT
+                ))
         } else {
-            OkHttpSardine(okHttpClientWithTrustedCertificates(certificates))
+            val sslContext = SSLContext.getInstance("TLS").apply {
+                init(null, arrayOf(trustManager), null)
+            }
+            builder.sslSocketFactory(sslContext.socketFactory, trustManager)
         }
+        return builder.build()
     }
 
-    private fun okHttpClientWithTrustedCertificates(certificates: String): OkHttpClient {
-        val trustManager = trustManagerForCertificates(certificates)
-
-        val sslContext = SSLContext.getInstance("TLS").apply {
-            init(null, arrayOf(trustManager), null)
+    private fun x509TrustManager(certificates: String?): X509TrustManager {
+        TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm()).apply {
+            init(keyStore(certificates))
+            if (trustManagers.isNotEmpty() && trustManagers[0] is X509TrustManager) {
+                return trustManagers[0] as X509TrustManager
+            }
+            throw IllegalStateException("Unexpected default trust manager: " + Arrays.toString(trustManagers))
         }
-
-        val sslSocketFactory = sslContext.socketFactory
-
-        return OkHttpClient.Builder()
-                .sslSocketFactory(sslSocketFactory, trustManager)
-                .build()
     }
 
-    private fun trustManagerForCertificates(str: String): X509TrustManager {
-        // Read certificates
-        val certificates = Buffer().writeUtf8(str).inputStream().use { stream ->
+    private fun keyStore(certificates: String?): KeyStore? {
+        if (certificates.isNullOrEmpty()) {
+            return null
+        }
+        val certs = Buffer().writeUtf8(certificates).inputStream().use { stream ->
             CertificateFactory.getInstance("X.509").generateCertificates(stream)
         }
-
-//        require(!certificates.isEmpty()) {
-//            "Expected non-empty set of trusted certificates"
-//        }
-
-        // Create new key store
         val password = "password".toCharArray() // Any password will work
         val keyStore = newEmptyKeyStore(password)
-        for ((index, certificate) in certificates.withIndex()) {
+        for ((index, cert) in certs.withIndex()) {
             val certificateAlias = index.toString()
-            keyStore.setCertificateEntry(certificateAlias, certificate)
-        }
-
-        val trustManagerFactory = TrustManagerFactory.getInstance(
-                TrustManagerFactory.getDefaultAlgorithm()
-        ).apply {
-            init(keyStore)
+            keyStore.setCertificateEntry(certificateAlias, cert)
         }
-
-        val trustManagers = trustManagerFactory.trustManagers
-        check(trustManagers.size == 1 && trustManagers[0] is X509TrustManager) {
-            "Unexpected default trust managers: ${Arrays.toString(trustManagers)}"
-        }
-
-        return trustManagers[0] as X509TrustManager
+        return keyStore
     }
 
     private fun newEmptyKeyStore(password: CharArray): KeyStore {
diff --git a/app/src/main/java/com/orgzly/android/util/TLSSocketFactory.kt b/app/src/main/java/com/orgzly/android/util/TLSSocketFactory.kt
new file mode 100644
index 000000000..4c9ab06e5
--- /dev/null
+++ b/app/src/main/java/com/orgzly/android/util/TLSSocketFactory.kt
@@ -0,0 +1,85 @@
+package com.orgzly.android.util
+
+import java.io.IOException
+import java.net.InetAddress
+import java.net.Socket
+import java.net.UnknownHostException
+import javax.net.ssl.SSLContext
+import javax.net.ssl.SSLSocket
+import javax.net.ssl.SSLSocketFactory
+import javax.net.ssl.X509TrustManager
+
+
+class TLSSocketFactory (trustManager: X509TrustManager) : SSLSocketFactory() {
+    private val internalSSLSocketFactory: SSLSocketFactory
+
+    init {
+        val context = SSLContext.getInstance("TLS")
+        context.init(null, arrayOf(trustManager), null)
+        internalSSLSocketFactory = context.socketFactory
+    }
+
+    override fun getDefaultCipherSuites(): Array<String> {
+        return internalSSLSocketFactory.defaultCipherSuites
+    }
+
+    override fun getSupportedCipherSuites(): Array<String> {
+        return internalSSLSocketFactory.supportedCipherSuites
+    }
+
+    @Throws(IOException::class)
+    override fun createSocket(s: Socket, host: String, port: Int, autoClose: Boolean): Socket {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(s, host, port, autoClose))
+    }
+
+    @Throws(IOException::class, UnknownHostException::class)
+    override fun createSocket(host: String, port: Int): Socket {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(host, port))
+    }
+
+    @Throws(IOException::class)
+    override fun createSocket(
+        host: String,
+        port: Int,
+        localHost: InetAddress,
+        localPort: Int
+    ): Socket {
+        return enableTLSOnSocket(
+            internalSSLSocketFactory.createSocket(
+                host,
+                port,
+                localHost,
+                localPort
+            )
+        )
+    }
+
+    @Throws(IOException::class)
+    override fun createSocket(host: InetAddress, port: Int): Socket {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(host, port))
+    }
+
+    @Throws(IOException::class)
+    override fun createSocket(
+        address: InetAddress,
+        port: Int,
+        localAddress: InetAddress,
+        localPort: Int
+    ): Socket {
+        return enableTLSOnSocket(
+            internalSSLSocketFactory.createSocket(
+                address,
+                port,
+                localAddress,
+                localPort
+            )
+        )
+    }
+
+    private fun enableTLSOnSocket(socket: Socket): Socket {
+        if (socket is SSLSocket) {
+            socket.enabledProtocols = arrayOf("TLSv1.2", "TLSv1.1")
+        }
+        return socket
+    }
+}
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 5bf8f55c1..bc85b11fe 100644
--- a/build.gradle
+++ b/build.gradle
@@ -59,7 +59,7 @@ buildscript {
 
     versions.glide = '4.10.0'
 
-    versions.sardine = '0.5'
+    versions.sardine = '0.4'
 
     versions.jgit = '4.4.1.201607150455-r'