diff --git a/models/quad_plane.obj b/models/quad_plane.obj
new file mode 100644
index 00000000..761b16c9
--- /dev/null
+++ b/models/quad_plane.obj
@@ -0,0 +1,25 @@
+# a 2x2 quad plane
+o Plane
+v -0.5 0 -0.5
+v 0 0 -0.5
+v 0.5 0 -0.5
+v 0.5 0 0
+v 0.5 0 0.5
+v 0 0 0.5
+v -0.5 0 0.5
+v -0.5 0 0
+v 0 0 0
+vn 0 1 0
+vt 0 1
+vt 0 0.5
+vt 0.5 0.5
+vt 0.5 1
+vt 0 0
+vt 0.5 0
+vt 1 0.5
+vt 1 1
+vt 1 0
+f 1/1/1 8/2/1 9/3/1 2/4/1
+f 8/2/1 7/5/1 6/6/1 9/3/1
+f 2/4/1 9/3/1 4/7/1 3/8/1
+f 9/3/1 6/6/1 5/9/1 4/7/1
diff --git a/models/variable_facevert_count.obj b/models/variable_facevert_count.obj
new file mode 100644
index 00000000..2b364980
--- /dev/null
+++ b/models/variable_facevert_count.obj
@@ -0,0 +1,36 @@
+# three polygonal faces with varying number of vertices.
+o Mesh
+v -1.04 0 -0.4
+v -1.47301 0 0.35
+v -0.606987 0 0.35
+v -0.5 0 -0.5
+v 0.5 0 -0.5
+v 0.5 0 0.5
+v -0.5 0 0.5
+v 1.15 0 -0.5
+v 0.796447 0 -0.353553
+v 0.65 0 0
+v 0.796447 0 0.353553
+v 1.15 0 0.5
+v 1.50355 0 0.353553
+v 1.65 0 0
+v 1.50355 0 -0.353553
+vn 0 1 0
+vt 0.091042 0.988145
+vt 0.32738 0.578795
+vt 0.563719 0.988145
+vt 0.01 0.5558
+vt 0.01 0.01
+vt 0.5558 0.01
+vt 0.5558 0.5558
+vt 0.99 0.842308
+vt 0.842308 0.99
+vt 0.633439 0.99
+vt 0.485746 0.842308
+vt 0.485746 0.633439
+vt 0.633439 0.485746
+vt 0.842308 0.485746
+vt 0.99 0.633439
+f 1/1/1 2/2/1 3/3/1
+f 4/4/1 7/5/1 6/6/1 5/7/1
+f 8/8/1 9/9/1 10/10/1 11/11/1 12/12/1 13/13/1 14/14/1 15/15/1
diff --git a/source/test/test.cpp b/source/test/test.cpp
index 4c94e583..274be996 100644
--- a/source/test/test.cpp
+++ b/source/test/test.cpp
@@ -71,7 +71,7 @@ bool generateAtlas(const char *filename, bool useUvMesh, AtlasResult *result)
 	std::vector<tinyobj::shape_t> shapes;
 	std::vector<tinyobj::material_t> materials;
 	std::string err;
-	if (!tinyobj::LoadObj(shapes, materials, err, filename, NULL, tinyobj::triangulation)) {
+	if (!tinyobj::LoadObj(shapes, materials, err, filename, NULL, 0)) {
 		logf("   [FAILED]: %s\n", err.c_str());
 		return false;
 	}
@@ -119,6 +119,11 @@ bool generateAtlas(const char *filename, bool useUvMesh, AtlasResult *result)
 			decl.indexCount = (int)objMesh.indices.size();
 			decl.indexData = objMesh.indices.data();
 			decl.indexFormat = xatlas::IndexFormat::UInt32;
+			if (objMesh.num_vertices.size() != objMesh.indices.size() / 3)
+			{
+				decl.faceVertexCount = objMesh.num_vertices.data();
+				decl.faceCount = (uint32_t)objMesh.num_vertices.size();
+			}
 			xatlas::AddMeshError error = xatlas::AddMesh(atlas, decl);
 			if (error != xatlas::AddMeshError::Success) {
 				xatlas::Destroy(atlas);
@@ -237,7 +242,7 @@ int main(int argc, char **argv)
 			ASSERT(result.chartCount == 2);
 		}
 		if (generateAtlas(MODEL_PATH "gazebo.obj", false, &result)) {
-			ASSERT(result.chartCount == 333);
+			ASSERT(result.chartCount == 332);
 		}
 		if (generateAtlas(MODEL_PATH "zero_area_face.obj", false, &result)) {
 			ASSERT(result.chartCount == 0);
@@ -245,6 +250,12 @@ int main(int argc, char **argv)
 		if (generateAtlas(MODEL_PATH "zero_length_edge.obj", false, &result)) {
 			ASSERT(result.chartCount == 1);
 		}
+		if (generateAtlas(MODEL_PATH "variable_facevert_count.obj", false, &result)) {
+			ASSERT(result.chartCount == 3);
+		}
+		if (generateAtlas(MODEL_PATH "quad_plane.obj", false, &result)) {
+			ASSERT(result.chartCount == 1);
+		}
 	}
 	return 0;
 }
diff --git a/source/xatlas/xatlas.cpp b/source/xatlas/xatlas.cpp
index 5c5c57ec..1f850ff9 100644
--- a/source/xatlas/xatlas.cpp
+++ b/source/xatlas/xatlas.cpp
@@ -9083,6 +9083,7 @@ AddMeshError AddMesh(Atlas *atlas, const MeshDecl &meshDecl, uint32_t meshCountH
 		meshPolygonMapping->triangleToPolygonMap.reserve(meshDecl.faceCount);
 		meshPolygonMapping->triangleToPolygonIndicesMap.reserve(meshDecl.indexCount);
 	}
+	uint32_t firstIndex = 0;
 	const uint32_t kMaxWarnings = 50;
 	uint32_t warningCount = 0;
 	internal::Array<uint32_t> triIndices;
@@ -9093,7 +9094,7 @@ AddMeshError AddMesh(Atlas *atlas, const MeshDecl &meshDecl, uint32_t meshCountH
 		uint32_t polygon[UINT8_MAX];
 		for (uint32_t i = 0; i < faceVertexCount; i++) {
 			if (hasIndices) {
-				polygon[i] = DecodeIndex(meshDecl.indexFormat, meshDecl.indexData, meshDecl.indexOffset, face * faceVertexCount + i);
+				polygon[i] = DecodeIndex(meshDecl.indexFormat, meshDecl.indexData, meshDecl.indexOffset, firstIndex + i);
 				// Check if any index is out of range.
 				if (polygon[i] >= meshDecl.vertexCount) {
 					mesh->~Mesh();
@@ -9191,10 +9192,17 @@ AddMeshError AddMesh(Atlas *atlas, const MeshDecl &meshDecl, uint32_t meshCountH
 			if (meshPolygonMapping)
 				meshPolygonMapping->triangleToPolygonMap.push_back(face);
 		}
+		// For each triangle index, store original index location
 		if (meshPolygonMapping) {
 			for (uint32_t i = 0; i < triIndices.size(); i++)
-				meshPolygonMapping->triangleToPolygonIndicesMap.push_back(triIndices[i]);
+			{
+				uint32_t polygonIndex = 0;
+				for (polygonIndex; polygonIndex < faceVertexCount; polygonIndex++)
+					if (triIndices[i] == polygon[polygonIndex]) break;
+				meshPolygonMapping->triangleToPolygonIndicesMap.push_back(firstIndex+polygonIndex);
+			}
 		}
+		firstIndex += faceVertexCount;
 	}
 	if (warningCount > kMaxWarnings)
 		XA_PRINT("   %u additional warnings truncated\n", warningCount - kMaxWarnings);