diff --git a/Cocoa/Document.xib b/Cocoa/Document.xib
index b3066894..754e92fa 100644
--- a/Cocoa/Document.xib
+++ b/Cocoa/Document.xib
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="8191" systemVersion="14F27" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" customObjectInstantitationMethod="direct">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="9531" systemVersion="14F1713" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" customObjectInstantitationMethod="direct">
     <dependencies>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="8191"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="9531"/>
     </dependencies>
     <objects>
         <customObject id="-2" userLabel="File's Owner" customClass="Document">
@@ -26,10 +26,16 @@
                 <rect key="frame" x="0.0" y="0.0" width="160" height="144"/>
                 <autoresizingMask key="autoresizingMask"/>
                 <subviews>
-                    <openGLView colorSize="5bit_RGB_8bit_Alpha" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" id="uqf-pe-VAF" customClass="GBView">
+                    <customView id="KTk-4M-J7t" customClass="GBBorderView">
                         <rect key="frame" x="0.0" y="0.0" width="160" height="144"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
-                    </openGLView>
+                        <subviews>
+                            <openGLView colorSize="5bit_RGB_8bit_Alpha" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" id="uqf-pe-VAF" customClass="GBView">
+                                <rect key="frame" x="0.0" y="0.0" width="160" height="144"/>
+                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                            </openGLView>
+                        </subviews>
+                    </customView>
                 </subviews>
             </view>
             <connections>
diff --git a/Cocoa/GBBorderView.h b/Cocoa/GBBorderView.h
new file mode 100644
index 00000000..477add17
--- /dev/null
+++ b/Cocoa/GBBorderView.h
@@ -0,0 +1,5 @@
+#import <Cocoa/Cocoa.h>
+
+@interface GBBorderView : NSView
+
+@end
diff --git a/Cocoa/GBBorderView.m b/Cocoa/GBBorderView.m
new file mode 100644
index 00000000..c81adb4a
--- /dev/null
+++ b/Cocoa/GBBorderView.m
@@ -0,0 +1,11 @@
+#import "GBBorderView.h"
+
+@implementation GBBorderView
+
+- (void)drawRect:(NSRect)dirtyRect {
+    [[NSColor blackColor] setFill];
+    NSRectFill(dirtyRect);
+    [super drawRect:dirtyRect];
+}
+
+@end
diff --git a/Cocoa/GBView.m b/Cocoa/GBView.m
index 28224301..0b1261f2 100644
--- a/Cocoa/GBView.m
+++ b/Cocoa/GBView.m
@@ -87,6 +87,25 @@
     return self;
 }
 
+- (void)setFrame:(NSRect)frame
+{
+    frame = self.superview.frame;
+    double ratio = frame.size.width / frame.size.height;
+    if (ratio >= 160.0/144.0) {
+        double new_width = round(frame.size.height / 144.0 * 160.0);
+        frame.origin.x = floor((frame.size.width - new_width) / 2);
+        frame.size.width = new_width;
+        frame.origin.y = 0;
+    }
+    else {
+        double new_height = round(frame.size.width / 160.0 * 144.0);
+        frame.origin.y = floor((frame.size.height - new_height) / 2);
+        frame.size.height = new_height;
+        frame.origin.x = 0;
+    }
+    [super setFrame:frame];
+}
+
 - (void)drawRect:(NSRect)dirtyRect {
     if (!self.shader) {
         self.shader = [[GBShader alloc] initWithName:[[NSUserDefaults standardUserDefaults] objectForKey:@"GBFilter"]];
@@ -110,7 +129,6 @@
     glFlush();
 }
 
-
 - (void) flip
 {
     current_buffer = (current_buffer + 1) % self.numberOfBuffers;