diff --git a/dependencies.gradle b/dependencies.gradle
index 24ae3b23..52463fc7 100644
--- a/dependencies.gradle
+++ b/dependencies.gradle
@@ -24,7 +24,7 @@ ext.versions = [
         kotlinxCoroutines    : "1.3.9",
         viewModelKtx         : "2.2.0",
 
-        retrofit             : "2.4.0",
+        retrofit             : "2.6.4",
         jackson              : "2.9.5",
         okhttp               : "3.12.13",
         semver               : "1.0.0",
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/EditServerFragment.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/EditServerFragment.kt
index 9b6c031e..12519813 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/EditServerFragment.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/EditServerFragment.kt
@@ -320,7 +320,7 @@ class EditServerFragment : Fragment(), OnBackPressedHandler {
                 // Execute a ping to retrieve the API version.
                 // This is accepted to fail if the authentication is incorrect yet.
                 var pingResponse = subsonicApiClient.api.ping().execute()
-                if (pingResponse?.body() != null) {
+                if (pingResponse.body() != null) {
                     val restApiVersion = pingResponse.body()!!.version.restApiVersion
                     currentServerSetting!!.minimumApiVersion = restApiVersion
                     Timber.i("Server minimum API version set to %s", restApiVersion)
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/ApiCallResponseChecker.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/ApiCallResponseChecker.kt
index 74baeec5..51bd4b0a 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/ApiCallResponseChecker.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/ApiCallResponseChecker.kt
@@ -26,7 +26,7 @@ class ApiCallResponseChecker(
         if (activeServerProvider.getActiveServer().minimumApiVersion == null) {
             try {
                 val response = subsonicAPIClient.api.ping().execute()
-                if (response?.body() != null) {
+                if (response.body() != null) {
                     val restApiVersion = response.body()!!.version.restApiVersion
                     Timber.i("Server minimum API version set to %s", restApiVersion)
                     activeServerProvider.setMinimumApiVersion(restApiVersion)