diff --git a/src/client/http/requestmanager/Libcurl.cpp b/src/client/http/requestmanager/Libcurl.cpp
index 121c5a747..22a87dbb6 100644
--- a/src/client/http/requestmanager/Libcurl.cpp
+++ b/src/client/http/requestmanager/Libcurl.cpp
@@ -371,11 +371,11 @@ namespace http
 			{
 #ifdef REQUEST_USE_CURL_OFFSET_T
 				curl_off_t total, done;
-				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_CONTENT_LENGTH_DOWNLOAD_T, &total));
+				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_CONTENT_LENGTH_DOWNLOAD_T, &total)); // stores -1 if unknown
 				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_SIZE_DOWNLOAD_T, &done));
 #else
 				double total, done;
-				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &total));
+				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &total)); // stores -1 if unknown
 				HandleCURLcode(curl_easy_getinfo(handle->curlEasy, CURLINFO_SIZE_DOWNLOAD, &done));
 #endif
 				handle->bytesTotal = int(total);
@@ -383,7 +383,7 @@ namespace http
 			}
 			else
 			{
-				handle->bytesTotal = 0;
+				handle->bytesTotal = -1;
 				handle->bytesDone = 0;
 			}
 		}
diff --git a/src/client/http/requestmanager/RequestManager.h b/src/client/http/requestmanager/RequestManager.h
index c7cbb1ee9..b199e1a92 100644
--- a/src/client/http/requestmanager/RequestManager.h
+++ b/src/client/http/requestmanager/RequestManager.h
@@ -37,7 +37,7 @@ namespace http
 		State state = ready;
 		std::mutex stateMx;
 		std::condition_variable stateCv;
-		std::atomic<int> bytesTotal = 0;
+		std::atomic<int> bytesTotal = -1;
 		std::atomic<int> bytesDone = 0;
 		int statusCode = 0;
 		ByteString responseData;
diff --git a/src/gui/update/UpdateActivity.cpp b/src/gui/update/UpdateActivity.cpp
index c75a6ab4c..e44beb58a 100644
--- a/src/gui/update/UpdateActivity.cpp
+++ b/src/gui/update/UpdateActivity.cpp
@@ -42,7 +42,14 @@ private:
 		{
 			int total, done;
 			std::tie(total, done) = request->CheckProgress();
-			notifyProgress(total ? done * 100 / total : 0);
+			if (total == -1)
+			{
+				notifyProgress(-1);
+			}
+			else
+			{
+				notifyProgress(total ? done * 100 / total : 0);
+			}
 			Platform::Millisleep(1);
 		}