diff --git a/src/logic/Preferences.swift b/src/logic/Preferences.swift
index 1a5c2107..477a0086 100644
--- a/src/logic/Preferences.swift
+++ b/src/logic/Preferences.swift
@@ -397,8 +397,8 @@ extension UserDefaults {
     }
 
     func cgfloat(_ key: String) -> CGFloat {
-        if let result = (NumberFormatter().number(from: string(key)).flatMap { CGFloat(truncating: $0) }) {
-            return result
+        if let intResult = Int(string(key)) {
+            return CGFloat(intResult)
         }
         removeObject(forKey: key)
         return cgfloat(key)
diff --git a/src/ui/main-window/ThumbnailsView.swift b/src/ui/main-window/ThumbnailsView.swift
index b3f48f6b..221255e9 100644
--- a/src/ui/main-window/ThumbnailsView.swift
+++ b/src/ui/main-window/ThumbnailsView.swift
@@ -59,7 +59,7 @@ class ThumbnailsView: NSVisualEffectView {
         var currentY = Preferences.interCellPadding
         var maxX = CGFloat(0)
         var maxY = currentY + height + Preferences.interCellPadding
-        scrollView.documentView!.subviews.removeAll()
+        var newViews = [ThumbnailView]()
         rows.removeAll()
         rows.append([ThumbnailView]())
         for (index, window) in Windows.list.enumerated() {
@@ -81,10 +81,11 @@ class ThumbnailsView: NSVisualEffectView {
                 currentX = projectedX
                 maxX = max(isLeftToRight ? currentX : widthMax - currentX, maxX)
             }
-            scrollView.documentView!.subviews.append(view)
+            newViews.append(view)
             rows[rows.count - 1].append(view)
             window.row = rows.count - 1
         }
+        scrollView.documentView!.subviews = newViews
         return (maxX, maxY)
     }