diff --git a/Lib/fontTools/varLib/interpolatable.py b/Lib/fontTools/varLib/interpolatable.py
index 41b710ccd..1b4164dea 100644
--- a/Lib/fontTools/varLib/interpolatable.py
+++ b/Lib/fontTools/varLib/interpolatable.py
@@ -808,8 +808,9 @@ def test_gen(
                         midVector = _contour_vector_from_stats(midStats)
                         midSize = midVector[0] * midVector[0]
 
-                        for overweight, problem_type in enumerate(("underweight", "overweight")):
-
+                        for overweight, problem_type in enumerate(
+                            ("underweight", "overweight")
+                        ):
                             if overweight:
                                 expectedSize = (size0 * size1) ** 0.5
                                 expectedSize = (size0 + size1) - expectedSize
@@ -825,9 +826,10 @@ def test_gen(
                                 size1,
                             )
                             if (
-                                (not overweight and expectedSize * tolerance > midSize + 1e-5)
-                                or
-                                (overweight and 1e-5 + expectedSize < midSize * tolerance)
+                                not overweight
+                                and expectedSize * tolerance > midSize + 1e-5
+                            ) or (
+                                overweight and 1e-5 + expectedSize < midSize * tolerance
                             ):
                                 try:
                                     if overweight:
@@ -1061,6 +1063,11 @@ def main(args=None):
         action="store",
         help="Output report in PDF format",
     )
+    parser.add_argument(
+        "--ps",
+        action="store",
+        help="Output report in PostScript format",
+    )
     parser.add_argument(
         "--html",
         action="store",
@@ -1463,6 +1470,18 @@ def main(args=None):
                 if not problems and not args.quiet:
                     pdf.draw_cupcake()
 
+        if args.ps:
+            log.info("Writing PS to %s", args.pdf)
+            from .interpolatablePlot import InterpolatablePS
+
+            with InterpolatablePS(args.ps, glyphsets=glyphsets, names=names) as ps:
+                ps.add_title_page(
+                    original_args_inputs, tolerance=tolerance, kinkiness=kinkiness
+                )
+                ps.add_problems(problems)
+                if not problems and not args.quiet:
+                    ps.draw_cupcake()
+
         if args.html:
             log.info("Writing HTML to %s", args.html)
             from .interpolatablePlot import InterpolatableSVG
diff --git a/Lib/fontTools/varLib/interpolatablePlot.py b/Lib/fontTools/varLib/interpolatablePlot.py
index c492dea42..8d5d74879 100644
--- a/Lib/fontTools/varLib/interpolatablePlot.py
+++ b/Lib/fontTools/varLib/interpolatablePlot.py
@@ -513,7 +513,11 @@ class InterpolatablePlot:
                 midway_glyphset,
                 glyphname,
                 [{"type": "midway"}]
-                + [p for p in problems if p["type"] in ("kink", "underweight", "overweight")],
+                + [
+                    p
+                    for p in problems
+                    if p["type"] in ("kink", "underweight", "overweight")
+                ],
                 None,
                 x=x,
                 y=y,