diff --git a/ports/unix/variants/coverage/manifest.py b/ports/unix/variants/coverage/manifest.py
index 6111050884..7c3d9a6b64 100644
--- a/ports/unix/variants/coverage/manifest.py
+++ b/ports/unix/variants/coverage/manifest.py
@@ -1,2 +1,3 @@
 freeze_as_str("frzstr")
 freeze_as_mpy("frzmpy")
+freeze_mpy("$(MPY_DIR)/tests/frozen")
diff --git a/tests/unix/extra_coverage.py b/tests/unix/extra_coverage.py
index bb22485026..00226a68e6 100644
--- a/tests/unix/extra_coverage.py
+++ b/tests/unix/extra_coverage.py
@@ -96,3 +96,8 @@ import frzmpy3
 from frzqstr import returns_NULL
 
 print(returns_NULL())
+
+# test for freeze_mpy
+import frozentest
+
+print(frozentest.__file__)
diff --git a/tests/unix/extra_coverage.py.exp b/tests/unix/extra_coverage.py.exp
index 4d6e1e0856..2941154556 100644
--- a/tests/unix/extra_coverage.py.exp
+++ b/tests/unix/extra_coverage.py.exp
@@ -199,3 +199,13 @@ X
 '\x1b'
 b'\x00\xff'
 NULL
+uPy
+a long string that is not interned
+a string that has unicode αβγ chars
+b'bytes 1234\x01'
+123456789
+0
+1
+2
+3
+frozentest.py
diff --git a/tools/makemanifest.py b/tools/makemanifest.py
index 9dd8815aac..b2e4f7d844 100644
--- a/tools/makemanifest.py
+++ b/tools/makemanifest.py
@@ -210,9 +210,9 @@ def main():
                 ts_outfile = get_timestamp(outfile)
             mpy_files.append(outfile)
         else:
-            assert kind == manifestfile.KIND_FREEZE_MPY
-            mpy_files.append(full_path)
-            ts_outfile = timestamp
+            assert result.kind == manifestfile.KIND_FREEZE_MPY
+            mpy_files.append(result.full_path)
+            ts_outfile = result.timestamp
         ts_newest = max(ts_newest, ts_outfile)
 
     # Check if output file needs generating
diff --git a/tools/manifestfile.py b/tools/manifestfile.py
index 84c79ed82b..a4d056137f 100644
--- a/tools/manifestfile.py
+++ b/tools/manifestfile.py
@@ -394,28 +394,37 @@ class ManifestFile:
         `opt` is the optimisation level to pass to mpy-cross when compiling .py
         to .mpy.
         """
-        self._freeze_internal(path, script, exts=(".py", ".mpy"), kind=KIND_FREEZE_AUTO, opt=opt)
+        self._freeze_internal(
+            path,
+            script,
+            exts=(
+                ".py",
+                ".mpy",
+            ),
+            kind=KIND_FREEZE_AUTO,
+            opt=opt,
+        )
 
     def freeze_as_str(self, path):
         """
         Freeze the given `path` and all .py scripts within it as a string,
         which will be compiled upon import.
         """
-        self._search(path, None, None, exts=(".py"), kind=KIND_FREEZE_AS_STR)
+        self._search(path, None, None, exts=(".py",), kind=KIND_FREEZE_AS_STR)
 
     def freeze_as_mpy(self, path, script=None, opt=None):
         """
         Freeze the input (see above) by first compiling the .py scripts to
         .mpy files, then freezing the resulting .mpy files.
         """
-        self._freeze_internal(path, script, exts=(".py"), kind=KIND_FREEZE_AS_MPY, opt=opt)
+        self._freeze_internal(path, script, exts=(".py",), kind=KIND_FREEZE_AS_MPY, opt=opt)
 
     def freeze_mpy(self, path, script=None, opt=None):
         """
         Freeze the input (see above), which must be .mpy files that are
         frozen directly.
         """
-        self._freeze_internal(path, script, exts=(".mpy"), kind=KIND_FREEZE_MPY, opt=opt)
+        self._freeze_internal(path, script, exts=(".mpy",), kind=KIND_FREEZE_MPY, opt=opt)
 
 
 # Generate a temporary file with a line appended to the end that adds __version__.