diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index abdb4aebb625f..a1dc70397fbb9 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -148,7 +148,7 @@ cdef inline _Timestamp create_timestamp_from_ts(
     return ts_base
 
 
-def _unpickle_timestamp(value, freq, tz, reso):
+def _unpickle_timestamp(value, freq, tz, reso=NPY_FR_ns):
     # GH#41949 dont warn on unpickle if we have a freq
     if reso == NPY_FR_ns:
         ts = Timestamp(value, tz=tz)
diff --git a/pandas/tests/io/data/legacy_pickle/1.4.2/1.4.2_x86_64_linux_3.9.7.pickle b/pandas/tests/io/data/legacy_pickle/1.4.2/1.4.2_x86_64_linux_3.9.7.pickle
new file mode 100644
index 0000000000000..403ccf99c06d1
Binary files /dev/null and b/pandas/tests/io/data/legacy_pickle/1.4.2/1.4.2_x86_64_linux_3.9.7.pickle differ