diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index a769bbb081398..72cc33fa2002c 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -30,7 +30,7 @@ cdef extern from "src/datetime/np_datetime.h":
                                            npy_datetimestruct *d) nogil
 
 cimport util
-from util cimport is_period_object, is_string_object
+from util cimport is_period_object, is_string_object, is_offset_object
 
 from timestamps import Timestamp, maybe_integer_op_deprecated
 from timezones cimport is_utc, is_tzlocal, get_dst_info
@@ -1442,7 +1442,7 @@ def extract_ordinals(object[:] values, freq):
         int64_t[:] ordinals = np.empty(n, dtype=np.int64)
         object p
 
-    freqstr = Period._maybe_convert_freq(freq).freqstr
+    freq = Period._maybe_convert_freq(freq)
 
     for i in range(n):
         p = values[i]
@@ -1453,8 +1453,8 @@ def extract_ordinals(object[:] values, freq):
             try:
                 ordinals[i] = p.ordinal
 
-                if p.freqstr != freqstr:
-                    msg = DIFFERENT_FREQ_INDEX.format(freqstr, p.freqstr)
+                if p.freqstr != freq.freqstr:
+                    msg = DIFFERENT_FREQ_INDEX.format(freq.freqstr, p.freqstr)
                     raise IncompatibleFrequency(msg)
 
             except AttributeError:
@@ -1567,12 +1567,12 @@ cdef class _Period(object):
 
     @classmethod
     def _maybe_convert_freq(cls, object freq):
+        if not is_offset_object(freq):
+            if isinstance(freq, (int, tuple)):
+                code, stride = get_freq_code(freq)
+                freq = get_freq_str(code, stride)
 
-        if isinstance(freq, (int, tuple)):
-            code, stride = get_freq_code(freq)
-            freq = get_freq_str(code, stride)
-
-        freq = to_offset(freq)
+            freq = to_offset(freq)
 
         if freq.n <= 0:
             raise ValueError('Frequency must be positive, because it'