diff --git a/aegisub/src/dialog_detached_video.cpp b/aegisub/src/dialog_detached_video.cpp
index 2195ee161..d3d5a47ce 100644
--- a/aegisub/src/dialog_detached_video.cpp
+++ b/aegisub/src/dialog_detached_video.cpp
@@ -51,7 +51,7 @@
 
 ///////////////
 // Constructor
-DialogDetachedVideo::DialogDetachedVideo(FrameMain *par)
+DialogDetachedVideo::DialogDetachedVideo(FrameMain *par, const wxSize &initialDisplaySize)
 //: wxFrame(par,-1,_("Detached Video"))
 : wxDialog(par,-1,_T("Detached Video"),wxDefaultPosition,wxSize(400,300),wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER | wxMAXIMIZE_BOX | wxMINIMIZE_BOX | wxWANTS_CHARS)
 {
@@ -77,6 +77,7 @@ DialogDetachedVideo::DialogDetachedVideo(FrameMain *par)
 	// Video area;
 	videoBox = new VideoBox(panel, true);
 	videoBox->videoDisplay->freeSize = true;
+	videoBox->videoDisplay->SetClientSize(initialDisplaySize);
 	videoBox->videoSlider->grid = par->SubsBox;
 
 	// Set sizer
diff --git a/aegisub/src/dialog_detached_video.h b/aegisub/src/dialog_detached_video.h
index e999d5688..6457a30f2 100644
--- a/aegisub/src/dialog_detached_video.h
+++ b/aegisub/src/dialog_detached_video.h
@@ -58,7 +58,7 @@ private:
 	void OnMove(wxMoveEvent &event);
 
 public:
-	DialogDetachedVideo(FrameMain *parent);
+	DialogDetachedVideo(FrameMain *parent, const wxSize &initialDisplaySize);
 	~DialogDetachedVideo();
 
 	DECLARE_EVENT_TABLE()
diff --git a/aegisub/src/frame_main.cpp b/aegisub/src/frame_main.cpp
index 7d1bf55e3..349c08508 100644
--- a/aegisub/src/frame_main.cpp
+++ b/aegisub/src/frame_main.cpp
@@ -1178,7 +1178,7 @@ void FrameMain::OpenHelp(wxString page) {
 void FrameMain::DetachVideo(bool detach) {
 	if (detach) {
 		if (!detachedVideo) {
-			detachedVideo = new DialogDetachedVideo(this);
+			detachedVideo = new DialogDetachedVideo(this, videoBox->videoDisplay->GetClientSize());
 			detachedVideo->Show();
 		}
 	}