diff --git a/examples/glFVarViewer/init_shapes.h b/examples/glFVarViewer/init_shapes.h
index 5cb1c370..2996c699 100644
--- a/examples/glFVarViewer/init_shapes.h
+++ b/examples/glFVarViewer/init_shapes.h
@@ -61,6 +61,7 @@ static void initShapes() {
     g_defaultShapes.push_back( ShapeDesc("catmark_fvar_bound1",      catmark_fvar_bound1,      kCatmark ) );
     g_defaultShapes.push_back( ShapeDesc("catmark_fvar_bound2",      catmark_fvar_bound2,      kCatmark ) );
     g_defaultShapes.push_back( ShapeDesc("catmark_fvar_bound3",      catmark_fvar_bound3,      kCatmark ) );
+    g_defaultShapes.push_back( ShapeDesc("catmark_fvar_bound4",      catmark_fvar_bound4,      kCatmark ) );
     g_defaultShapes.push_back( ShapeDesc("catmark_fvar_project0",    catmark_fvar_project0,    kCatmark ) );
     g_defaultShapes.push_back( ShapeDesc("catmark_gregory_test1",    catmark_gregory_test1,    kCatmark ) );
     g_defaultShapes.push_back( ShapeDesc("catmark_gregory_test2",    catmark_gregory_test2,    kCatmark ) );
diff --git a/opensubdiv/far/patchTableFactory.cpp b/opensubdiv/far/patchTableFactory.cpp
index 2058e4ff..55dcdf80 100644
--- a/opensubdiv/far/patchTableFactory.cpp
+++ b/opensubdiv/far/patchTableFactory.cpp
@@ -674,13 +674,23 @@ PatchTableFactory::BuilderContext::GetRegularPatchBoundaryMask(
     //  patch, and so both of its neighboring corners need to be re-interpreted as
     //  boundaries.
     //
-    //  With the introduction of inf-sharp patches, this may soon change...
+    //  With the introduction of sharp irregular patches, we are now better off
+    //  using irregular patches where appropriate, which will simplify the following
+    //  when this patch was already determined to be regular...
     //
-    if (fTag._nonManifold && (fvcRefiner < 0)) {
+    if (fTag._nonManifold) {
         if (vTags[0]._nonManifold) vBoundaryMask |= (1 << 0) | (vTags[0]._infSharp ? 10 : 0);
         if (vTags[1]._nonManifold) vBoundaryMask |= (1 << 1) | (vTags[1]._infSharp ?  5 : 0);
         if (vTags[2]._nonManifold) vBoundaryMask |= (1 << 2) | (vTags[2]._infSharp ? 10 : 0);
         if (vTags[3]._nonManifold) vBoundaryMask |= (1 << 3) | (vTags[3]._infSharp ?  5 : 0);
+
+        //  Force adjacent edges as boundaries if only one vertex in the resulting mask
+        //  (which would be an irregular boundary for Catmark, but not Loop):
+        if ((vBoundaryMask == (1 << 0)) || (vBoundaryMask == (1 << 2))) {
+            vBoundaryMask |= 10;
+        } else if ((vBoundaryMask == (1 << 1)) || (vBoundaryMask == (1 << 3))) {
+            vBoundaryMask |= 5;
+        }
     }
 
     //  Convert directly from a vertex- to edge-mask (no need to inspect edges):
diff --git a/regression/shapes/all.h b/regression/shapes/all.h
index a8fab5e7..813c44c9 100644
--- a/regression/shapes/all.h
+++ b/regression/shapes/all.h
@@ -49,6 +49,7 @@
 #include "catmark_fvar_bound1.h"
 #include "catmark_fvar_bound2.h"
 #include "catmark_fvar_bound3.h"
+#include "catmark_fvar_bound4.h"
 #include "catmark_fvar_project0.h"
 #include "catmark_gregory_test0.h"
 #include "catmark_gregory_test1.h"
diff --git a/regression/shapes/catmark_fan.h b/regression/shapes/catmark_fan.h
index 6b48952b..21bbdc30 100644
--- a/regression/shapes/catmark_fan.h
+++ b/regression/shapes/catmark_fan.h
@@ -1,5 +1,5 @@
 //
-//   Copyright 2013 Pixar
+//   Copyright 2016 Dreamworks
 //
 //   Licensed under the Apache License, Version 2.0 (the "Apache License")
 //   with the following modification; you may not use this file except in
@@ -25,27 +25,41 @@
 static const std::string catmark_fan =
 "# This file uses centimeters as units for non-parametric coordinates.\n"
 "\n"
-"v -1.000000 0.000000 -1.000000\n"
-"v -1.000000 0.000000 0.000000\n"
-"v 0.000000 0.000000 0.000000\n"
-"v 0.000000 0.000000 -1.000000\n"
-"v 1.000000 0.000000 0.000000\n"
-"v 1.000000 0.000000 -1.000000\n"
-"v 0.000000 1.000000 0.000000\n"
-"v 0.000000 1.000000 -1.000000\n"
-"vt 0.000000 0.000000\n"
-"vt 1.000000 0.000000\n"
-"vt 1.000000 1.000000\n"
-"vt 0.000000 1.000000\n"
-"vt 0.000000 0.000000\n"
-"vt 1.000000 0.000000\n"
-"vt 1.000000 1.000000\n"
-"vt 0.000000 1.000000\n"
-"vt 0.000000 0.000000\n"
-"vt 1.000000 0.000000\n"
-"vt 1.000000 1.000000\n"
-"vt 0.000000 1.000000\n"
-"f 1/1 2/2 3/3 4/4\n"
-"f 4/5 3/6 5/7 6/8\n"
-"f 4/9 3/10 7/11 8/12\n"
+"# This file uses centimeters as units for non-parametric coordinates.\n"
+"v  0.0   0   1.0\n"
+"v -0.5   0   0.5\n"
+"v  0.5   0   0.5\n"
+"v -1.0   0   0.0\n"
+"v  1.0   0   0.0\n"
+"v -1.5   0  -0.5\n"
+"v  1.5   0  -0.5\n"
+"v -1.0   0  -1.0\n"
+"v -0.5   0  -0.5\n"
+"v  0.0   0   0.0\n"
+"v  0.5   0  -0.5\n"
+"v  1.0   0  -1.0\n"
+"v -1.0  .5  -1.0\n"
+"v -0.5  .5  -0.5\n"
+"v  0.0  .5   0.0\n"
+"v  0.5  .5  -0.5\n"
+"v  1.0  .5  -1.0\n"
+"v -1.0 -.5  -1.0\n"
+"v -0.5 -.5  -0.5\n"
+"v  0.0 -.5   0.0\n"
+"v  0.5 -.5  -0.5\n"
+"v  1.0 -.5  -1.0\n"
+"f   1   2  10   3\n"
+"f   2   4   9  10\n"
+"f   4   6   8   9\n"
+"f   5   3  10  11\n"
+"f   7   5  11  12\n"
+"f   8   9  14  13\n"
+"f   9  10  15  14\n"
+"f  10  11  16  15\n"
+"f  11  12  17  16\n"
+"f   9   8  18  19\n"
+"f  10   9  19  20\n"
+"f  11  10  20  21\n"
+"f  12  11  21  22\n"
+"t interpolateboundary 1/0/0 1\n"
 "\n";
diff --git a/regression/shapes/catmark_fvar_bound4.h b/regression/shapes/catmark_fvar_bound4.h
new file mode 100644
index 00000000..3b7b0de5
--- /dev/null
+++ b/regression/shapes/catmark_fvar_bound4.h
@@ -0,0 +1,51 @@
+//
+//   Copyright 2016 Dreamworks
+//
+//   Licensed under the Apache License, Version 2.0 (the "Apache License")
+//   with the following modification; you may not use this file except in
+//   compliance with the Apache License and the following modification to it:
+//   Section 6. Trademarks. is deleted and replaced with:
+//
+//   6. Trademarks. This License does not grant permission to use the trade
+//      names, trademarks, service marks, or product names of the Licensor
+//      and its affiliates, except as required to comply with Section 4(c) of
+//      the License and to reproduce the content of the NOTICE file.
+//
+//   You may obtain a copy of the Apache License at
+//
+//       http://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the Apache License with the above modification is
+//   distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+//   KIND, either express or implied. See the Apache License for the specific
+//   language governing permissions and limitations under the Apache License.
+//
+
+static const std::string catmark_fvar_bound4 =
+"v -0.5  0.0 -0.5\n"
+"v  0.0  0.0 -0.5\n"
+"v  0.5  0.0 -0.5\n"
+"v -0.5  0.0  0.0\n"
+"v  0.0 -0.5  0.0\n"
+"v  0.5  0.0  0.0\n"
+"v -0.5  0.0  0.5\n"
+"v  0.0  0.0  0.5\n"
+"v  0.5  0.0  0.5\n"
+"vt 0.1 0.1\n"
+"vt 0.5 0.0\n"
+"vt 1.0 0.1\n"
+"vt 0.0 0.5\n"
+"vt 0.6 0.6\n"
+"vt 1.0 0.4\n"
+"vt 1.0 0.6\n"
+"vt 0.1 1.0\n"
+"vt 0.4 1.0\n"
+"vt 0.6 1.0\n"
+"vt 1.0 1.0\n"
+"f 1/1  2/2  5/5  4/4\n"
+"f 2/2  3/3  6/6  5/5\n"
+"f 4/4  5/5  8/9  7/8\n"
+"f 5/5  6/7  9/11 8/10\n"
+"t interpolateboundary 1/0/0 1\n"
+;