diff --git a/PyPDF2/_cmap.py b/PyPDF2/_cmap.py
index 2a9e2f0d2..05dea9bfb 100644
--- a/PyPDF2/_cmap.py
+++ b/PyPDF2/_cmap.py
@@ -205,6 +205,8 @@ def parse_to_unicode(
 
 def prepare_cm(ft: DictionaryObject) -> bytes:
     cm: bytes = cast(DecodedStreamObject, ft["/ToUnicode"]).get_data()
+    if isinstance(cm, str):
+        cm = cm.encode()
     # we need to prepare cm before due to missing return line in pdf printed to pdf from word
     cm = (
         cm.strip()
diff --git a/tests/test_cmap.py b/tests/test_cmap.py
index df472da6c..fd63fdd0e 100644
--- a/tests/test_cmap.py
+++ b/tests/test_cmap.py
@@ -84,3 +84,10 @@ def test_iss1370():
     name = "cmap1370.pdf"
     reader = PdfReader(BytesIO(get_pdf_from_url(url, name=name)))
     reader.pages[0].extract_text()
+
+
+def test_iss1370():
+    url = "https://github.com/py-pdf/PyPDF2/files/9712729/02voc.pdf"
+    name = "02voc.pdf"
+    reader = PdfReader(BytesIO(get_pdf_from_url(url, name=name)))
+    reader.pages[2].extract_text()