diff --git a/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/CookieNonceAuthenticator.kt b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/CookieNonceAuthenticator.kt
index 75a60c15a4..6a7710b6a6 100644
--- a/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/CookieNonceAuthenticator.kt
+++ b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/CookieNonceAuthenticator.kt
@@ -10,7 +10,6 @@ import org.wordpress.android.fluxc.network.rest.wpapi.Nonce.FailedRequest
 import org.wordpress.android.fluxc.network.rest.wpapi.Nonce.Unknown
 import org.wordpress.android.fluxc.persistence.SiteSqlUtils
 import org.wordpress.android.fluxc.tools.CoroutineEngine
-import org.wordpress.android.fluxc.utils.extensions.slashJoin
 import org.wordpress.android.util.AppLog
 import org.wordpress.android.util.UrlUtils
 import javax.inject.Inject
@@ -135,7 +134,7 @@ class CookieNonceAuthenticator @Inject constructor(
         url: String
     ): String {
         return discoveryWPAPIRestClient.discoverWPAPIBaseURL(url) // discover rest api endpoint
-            ?: url.slashJoin("wp-json/") // fallback to ".../wp-json/" if discovery fails
+            ?: WPAPIDiscoveryUtils.buildDefaultRESTBaseUrl(url)
     }
 
     sealed interface CookieNonceAuthenticationResult {
diff --git a/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/WPAPIDiscoveryUtils.kt b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/WPAPIDiscoveryUtils.kt
new file mode 100644
index 0000000000..329cd64a57
--- /dev/null
+++ b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/WPAPIDiscoveryUtils.kt
@@ -0,0 +1,18 @@
+package org.wordpress.android.fluxc.network.rest.wpapi
+
+import org.wordpress.android.fluxc.utils.extensions.slashJoin
+import org.wordpress.android.util.UrlUtils
+
+internal object WPAPIDiscoveryUtils {
+    fun buildDefaultRESTBaseUrl(
+        url: String
+    ): String {
+        val urlWithoutScheme = UrlUtils.removeScheme(url)
+        val httpsUrl = UrlUtils.addUrlSchemeIfNeeded(urlWithoutScheme, true)
+
+        // TODO investigate the possibility to use `/?rest_route=` instead,
+        //  `/wp-json` works only when permalinks are enabled, where `/?rest_route=` works without them
+        // fallback to ".../wp-json/"
+        return httpsUrl.slashJoin("wp-json")
+    }
+}
diff --git a/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/site/SiteWPAPIRestClient.kt b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/site/SiteWPAPIRestClient.kt
index 2443f527f5..6b90b19004 100644
--- a/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/site/SiteWPAPIRestClient.kt
+++ b/fluxc/src/main/java/org/wordpress/android/fluxc/network/rest/wpapi/site/SiteWPAPIRestClient.kt
@@ -9,11 +9,11 @@ import org.wordpress.android.fluxc.network.discovery.DiscoveryUtils
 import org.wordpress.android.fluxc.network.discovery.DiscoveryWPAPIRestClient
 import org.wordpress.android.fluxc.network.discovery.RootWPAPIRestResponse
 import org.wordpress.android.fluxc.network.rest.wpapi.BaseWPAPIRestClient
+import org.wordpress.android.fluxc.network.rest.wpapi.WPAPIDiscoveryUtils
 import org.wordpress.android.fluxc.network.rest.wpapi.WPAPIGsonRequestBuilder
 import org.wordpress.android.fluxc.network.rest.wpapi.WPAPIResponse.Error
 import org.wordpress.android.fluxc.network.rest.wpapi.WPAPIResponse.Success
 import org.wordpress.android.fluxc.store.SiteStore.FetchWPAPISitePayload
-import org.wordpress.android.fluxc.utils.extensions.slashJoin
 import org.wordpress.android.util.UrlUtils
 import javax.inject.Inject
 import javax.inject.Named
@@ -102,6 +102,6 @@ class SiteWPAPIRestClient @Inject constructor(
         url: String
     ): String {
         return discoveryWPAPIRestClient.discoverWPAPIBaseURL(url) // discover rest api endpoint
-            ?: url.slashJoin("wp-json/") // fallback to ".../wp-json/" if discovery fails
+            ?: WPAPIDiscoveryUtils.buildDefaultRESTBaseUrl(url)
     }
 }