diff --git a/aegisub/libaegisub/include/libaegisub/background_runner.h b/aegisub/libaegisub/include/libaegisub/background_runner.h
index 09f374f55..7ae72e886 100644
--- a/aegisub/libaegisub/include/libaegisub/background_runner.h
+++ b/aegisub/libaegisub/include/libaegisub/background_runner.h
@@ -21,7 +21,9 @@
 #pragma once
 
 #ifndef LAGI_PRE
+#include <stdint.h>
 #include <string>
+
 #ifdef _WIN32
 #include <functional>
 #else
@@ -49,7 +51,7 @@ namespace agi {
 		/// Set an additional message associated with the task
 		virtual void SetMessage(std::string const& msg)=0;
 		/// Set the current task progress
-		virtual void SetProgress(int cur, int max)=0;
+		virtual void SetProgress(int64_t cur, int64_t max)=0;
 
 		/// @brief Log a message
 		///
diff --git a/aegisub/src/auto4_base.h b/aegisub/src/auto4_base.h
index fb74a035c..6fa3a3d65 100644
--- a/aegisub/src/auto4_base.h
+++ b/aegisub/src/auto4_base.h
@@ -148,7 +148,7 @@ namespace Automation4 {
 		void SetIndeterminate() { impl->SetIndeterminate(); }
 		void SetTitle(std::string const& title) { impl->SetTitle(title); }
 		void SetMessage(std::string const& msg) { impl->SetMessage(msg); }
-		void SetProgress(int cur, int max) { impl->SetProgress(cur, max); }
+		void SetProgress(int64_t cur, int64_t max) { impl->SetProgress(cur, max); }
 		void Log(std::string const& str) { impl->Log(str); }
 		bool IsCancelled() { return impl->IsCancelled(); }
 
diff --git a/aegisub/src/dialog_progress.cpp b/aegisub/src/dialog_progress.cpp
index 5ffc49b10..649e92c36 100644
--- a/aegisub/src/dialog_progress.cpp
+++ b/aegisub/src/dialog_progress.cpp
@@ -70,7 +70,7 @@ public:
 		SafeQueue(EVT_MESSAGE, lagi_wxString(msg));
 	}
 
-	void SetProgress(int cur, int max) {
+	void SetProgress(int64_t cur, int64_t max) {
 		SafeQueue(EVT_PROGRESS, int(double(cur) / max * 100));
 	}