diff --git a/java/libraries/opengl/src/processing/opengl/PGL.java b/java/libraries/opengl/src/processing/opengl/PGL.java
index 1d85d9dc8..a998dd75a 100644
--- a/java/libraries/opengl/src/processing/opengl/PGL.java
+++ b/java/libraries/opengl/src/processing/opengl/PGL.java
@@ -1288,6 +1288,11 @@ public class PGL {
     gl.glClearStencil(s);
   }
 
+  
+  public void glColorMask(boolean wr, boolean wg, boolean wb, boolean wa) {
+    gl.glColorMask(wr, wg, wb, wa);
+  }
+  
 
   public void glClearColor(float r, float g, float b, float a) {
     gl.glClearColor(r, g, b, a);
diff --git a/java/libraries/opengl/src/processing/opengl/PGraphicsOpenGL.java b/java/libraries/opengl/src/processing/opengl/PGraphicsOpenGL.java
index fd3e4fbf4..6b3ef5b3b 100644
--- a/java/libraries/opengl/src/processing/opengl/PGraphicsOpenGL.java
+++ b/java/libraries/opengl/src/processing/opengl/PGraphicsOpenGL.java
@@ -1645,7 +1645,21 @@ public class PGraphicsOpenGL extends PGraphics {
       }      
       
       popFramebuffer();
-
+      
+      // Make the offscreen color buffer opaque so it doesn't show      
+      // the background when drawn on the main surface. 
+      if (offscreenMultisample) {
+        pushFramebuffer();
+        setFramebuffer(offscreenFramebuffer);
+      }      
+      pgl.glColorMask(false, false, false, true);
+      pgl.glClearColor(0, 0, 0, 1);
+      pgl.glClear(PGL.GL_COLOR_BUFFER_BIT);
+      pgl.glColorMask(true, true, true, true);
+      if (offscreenMultisample) {
+        popFramebuffer();
+      }      
+      
       pgl.endOffscreenDraw(pgPrimary.clearColorBuffer0);
 
       pgPrimary.restoreGL();