diff --git a/spec/EntitiesSpec.xml b/spec/EntitiesSpec.xml
index 5aade74..fe5574b 100644
--- a/spec/EntitiesSpec.xml
+++ b/spec/EntitiesSpec.xml
@@ -493,7 +493,7 @@
     <Field Name="row_count" Code="71" Type="i16" DefaultValue="1" DisableWritingDefault="true" />
     <Field Name="column_spacing" Code="44" Type="f64" DefaultValue="0.0" DisableWritingDefault="true" />
     <Field Name="row_spacing" Code="45" Type="f64" DefaultValue="0.0" DisableWritingDefault="true" />
-    <Field Name="extrusion_direction" Code="210" Type="Vector" DefaultValue="Vector::z_axis()" CodeOverrides="210,220,230" MinVersion="R13" />
+    <Field Name="extrusion_direction" Code="210" Type="Vector" DefaultValue="Vector::z_axis()" CodeOverrides="210,220,230" MinVersion="R12" />
     <Field Name="__attributes_and_handles" Code="10" Type="(Attribute, Handle)" DefaultValue="vec![]" AllowMultiples="true" GenerateReader="false" GenerateWriter="false" />
     <WriteOrder>
       <WriteSpecificValue Code="100" Value='&amp;String::from("AcDbBlockReference")' MinVersion="R13" />
diff --git a/src/entity.rs b/src/entity.rs
index ff24a59..25b9166 100644
--- a/src/entity.rs
+++ b/src/entity.rs
@@ -1515,7 +1515,7 @@ impl Entity {
         }
         pairs.push(CodePair::new_i16(70, v.flags as i16));
         pairs.push(CodePair::new_f64(50, v.curve_fit_tangent_direction));
-        if version >= AcadVersion::R13 {
+        if version >= AcadVersion::R12 {
             if v.polyface_mesh_vertex_index1 != 0 {
                 pairs.push(CodePair::new_i16(71, v.polyface_mesh_vertex_index1 as i16));
             }
@@ -1572,7 +1572,13 @@ impl Entity {
                 for (v, vertex_handle) in &poly.__vertices_and_handles {
                     let mut v = v.clone();
                     v.set_is_3d_polyline_vertex(poly.is_3d_polyline());
-                    v.set_is_3d_polygon_mesh(poly.is_3d_polygon_mesh());
+                    if v.polyface_mesh_vertex_index1 == 0
+                        && v.polyface_mesh_vertex_index2 == 0
+                        && v.polyface_mesh_vertex_index3 == 0
+                        && v.polyface_mesh_vertex_index4 == 0
+                    {
+                        v.set_is_3d_polygon_mesh(poly.is_3d_polygon_mesh());
+                    }
                     let v = Entity {
                         common: EntityCommon {
                             handle: *vertex_handle,
@@ -2872,9 +2878,9 @@ mod tests {
     }
 
     #[test]
-    fn write_insert_no_extrusion_on_r12() {
+    fn write_insert_no_extrusion_on_r11() {
         let mut drawing = Drawing::new();
-        drawing.header.version = AcadVersion::R12;
+        drawing.header.version = AcadVersion::R11;
         let ins = Insert {
             extrusion_direction: Vector::new(1.0, 2.0, 3.0),
             ..Default::default()
@@ -2891,6 +2897,26 @@ mod tests {
         );
     }
 
+    #[test]
+    fn write_insert_extrusion_on_r12() {
+        let mut drawing = Drawing::new();
+        drawing.header.version = AcadVersion::R12;
+        let ins = Insert {
+            extrusion_direction: Vector::new(1.0, 2.0, 3.0),
+            ..Default::default()
+        };
+        let ent = Entity::new(EntityType::Insert(ins));
+        drawing.add_entity(ent);
+        assert_contains_pairs(
+            &drawing,
+            vec![
+                CodePair::new_f64(210, 1.0),
+                CodePair::new_f64(220, 2.0),
+                CodePair::new_f64(230, 3.0),
+            ],
+        );
+    }
+
     #[test]
     fn write_insert_extrusion_on_r13() {
         let mut drawing = Drawing::new();