diff --git a/window.c b/window.c
index 49288631..46bf64f2 100644
--- a/window.c
+++ b/window.c
@@ -1864,7 +1864,7 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
 		if (len == -1)
 		    return DefWindowProc(hwnd, message, wParam, lParam);
 
-		if (len > 0) {
+		if (len != 0) {
 		    /*
 		     * We need not bother about stdin backlogs
 		     * here, because in GUI PuTTY we can't do