diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -578,12 +578,13 @@ compatible_grf:
 
 /** Helper for scanning for files with GRF as extension */
 class GRFFileScanner : FileScanner {
-	uint next_update; ///< The next (realtime tick) we do update the screen.
+	std::chrono::steady_clock::time_point next_update; ///< The next moment we do update the screen.
 	uint num_scanned; ///< The number of GRFs we have scanned.
 
 public:
-	GRFFileScanner() : next_update(_realtime_tick), num_scanned(0)
+	GRFFileScanner() : num_scanned(0)
 	{
+		this->next_update = std::chrono::steady_clock::now();
 	}
 
 	bool AddFile(const std::string &filename, size_t basepath_length, const std::string &tar_filename) override;
@@ -634,7 +635,9 @@ bool GRFFileScanner::AddFile(const std::
 	}
 
 	this->num_scanned++;
-	if (this->next_update <= _realtime_tick) {
+	if (std::chrono::steady_clock::now() >= this->next_update) {
+		this->next_update = std::chrono::steady_clock::now() + std::chrono::milliseconds(MODAL_PROGRESS_REDRAW_TIMEOUT);
+
 		_modal_progress_work_mutex.unlock();
 		_modal_progress_paint_mutex.lock();
 
@@ -645,8 +648,6 @@ bool GRFFileScanner::AddFile(const std::
 
 		_modal_progress_work_mutex.lock();
 		_modal_progress_paint_mutex.unlock();
-
-		this->next_update = _realtime_tick + MODAL_PROGRESS_REDRAW_TIMEOUT;
 	}
 
 	if (!added) {