diff --git a/modules/juce_core/native/juce_mac_Network.mm b/modules/juce_core/native/juce_mac_Network.mm
index afde564fe6..77ee0f6afe 100644
--- a/modules/juce_core/native/juce_mac_Network.mm
+++ b/modules/juce_core/native/juce_mac_Network.mm
@@ -145,7 +145,8 @@ public:
         while (isThreadRunning() && ! initialised)
         {
             if (callback != nullptr)
-                callback (context, (int) latestTotalBytes, (int) [[request HTTPBody] length]);
+                if (! callback (context, (int) latestTotalBytes, (int) [[request HTTPBody] length]))
+                    return false;
 
             Thread::sleep (1);
         }
@@ -398,7 +399,8 @@ public:
         while (isThreadRunning() && ! initialised)
         {
             if (callback != nullptr)
-                callback (context, latestTotalBytes, (int) [[request HTTPBody] length]);
+                if (! callback (context, latestTotalBytes, (int) [[request HTTPBody] length]))
+                    return false;
 
             Thread::sleep (1);
         }