diff -r eb93feb6d3a3 -r 2f81758d1537 tests/subfiles.py
--- a/tests/subfiles.py	Mon Jun 24 00:28:37 2019 +0300
+++ b/tests/subfiles.py	Mon Jun 24 00:18:49 2019 +0300
@@ -102,6 +102,18 @@
                 scaling = scaling,
             )
 
+def subfile_references_with_invertnext(model):
+    import linetypes
+    has_invertnext = False
+    for element in model.body:
+        if isinstance(element, linetypes.MetaCommand) \
+        and element.text == 'BFC INVERTNEXT':
+            has_invertnext = True
+        else:
+            if isinstance(element, linetypes.SubfileReference):
+                yield element, has_invertnext
+            has_invertnext = False
+
 @problem_type('cyclical-reference',
     severity = 'hold',
     message = lambda chain:
@@ -132,6 +144,10 @@
             scaling = scaling_description(scaling_vector),
         ),
 )
+@problem_type('unnecessary-invertnext',
+    severity = 'warning',
+    message = 'flat subfile unnecessarily inverted using BFC INVERTNEXT'
+)
 def dependent_subfile_tests(model):
     '''
         Tests subfile references for such qualities that are dependent on the
@@ -141,7 +157,7 @@
     import filecache
     cache = filecache.SubfileCache(model.ldraw_directories)
     failed_subfiles = set()
-    for subfile_reference in model.subfile_references:
+    for subfile_reference, has_invertnext in subfile_references_with_invertnext(model):
         path = subfile_reference.subfile_path.lower()
         if path in failed_subfiles:
             # Already proven to be a bad apple, don't complain twice
@@ -165,6 +181,7 @@
                 )
                 failed_subfiles.add(path)
             else:
+                # Test for use of moved-to files
                 import re
                 match = re.search(r'^\~Moved(?: to (\w+))?$', subfile.description)
                 if match:
@@ -174,6 +191,7 @@
                         moved_file = path,
                         new_file = match.group(1),
                     )
+                # Test for scaling in flat direction
                 scaling_vector = subfile_reference.matrix.scaling_vector()
                 scaled_dimensions = {
                     dimension
@@ -192,6 +210,12 @@
                         scaled_flat_dimensions = scaled_flat_dimensions,
                         scaling_vector = scaling_vector,
                     )
+                # Test whether a flat subfile is inverted using invertnext
+                if has_invertnext and subfile.flatness:
+                    yield report_problem(
+                        'unnecessary-invertnext',
+                        bad_object = subfile_reference,
+                    )
 
 def dimensions_description(dimensions):
     if isinstance(dimensions, str):