diff --git a/netwerk/dns/TRRService.cpp b/netwerk/dns/TRRService.cpp
index b365e69c9671..853ef4e4de80 100644
--- a/netwerk/dns/TRRService.cpp
+++ b/netwerk/dns/TRRService.cpp
@@ -291,6 +291,16 @@ nsresult TRRService::ReadPrefs(const char* name) {
       !strcmp(name, kCaptivedetectCanonicalURL)) {
     nsAutoCString excludedDomains;
     Preferences::GetCString(TRR_PREF("excluded-domains"), excludedDomains);
+
+    mExcludedDomains.Clear();
+    nsCCharSeparatedTokenizer tokenizer(
+        excludedDomains, ',', nsCCharSeparatedTokenizer::SEPARATOR_OPTIONAL);
+    while (tokenizer.hasMoreTokens()) {
+      nsAutoCString token(tokenizer.nextToken());
+      LOG(("TRRService::ReadPrefs excluded-domains host:[%s]\n", token.get()));
+      mExcludedDomains.PutEntry(token);
+    }
+
     nsAutoCString canonicalSiteURL;
     Preferences::GetCString(kCaptivedetectCanonicalURL, canonicalSiteURL);
 
@@ -300,20 +310,9 @@ nsresult TRRService::ReadPrefs(const char* name) {
     if (NS_SUCCEEDED(rv)) {
       nsAutoCString host;
       uri->GetHost(host);
-
-      if (!excludedDomains.IsEmpty() && excludedDomains.Last() != ',') {
-        excludedDomains.AppendLiteral(",");
-      }
-      excludedDomains.Append(host);
-    }
-
-    mExcludedDomains.Clear();
-    nsCCharSeparatedTokenizer tokenizer(
-        excludedDomains, ',', nsCCharSeparatedTokenizer::SEPARATOR_OPTIONAL);
-    while (tokenizer.hasMoreTokens()) {
-      nsAutoCString token(tokenizer.nextToken());
-      LOG(("TRRService::ReadPrefs excluded-domains host:[%s]\n", token.get()));
-      mExcludedDomains.PutEntry(token);
+      LOG(("TRRService::ReadPrefs excluded-domains captive portal URL:[%s]\n",
+           host.get()));
+      mExcludedDomains.PutEntry(host);
     }
   }