diff --git a/src/docx/opc/phys_pkg.py b/src/docx/opc/phys_pkg.py
index 5ec32237c..ee31ac79d 100644
--- a/src/docx/opc/phys_pkg.py
+++ b/src/docx/opc/phys_pkg.py
@@ -1,7 +1,7 @@
 """Provides a general interface to a `physical` OPC package, such as a zip file."""
 
 import os
-from zipfile import ZIP_DEFLATED, ZipFile, is_zipfile
+from zipfile import ZIP_DEFLATED, BadZipFile, ZipFile, is_zipfile
 
 from docx.opc.exceptions import PackageNotFoundError
 from docx.opc.packuri import CONTENT_TYPES_URI
@@ -73,7 +73,12 @@ class _ZipPkgReader(PhysPkgReader):
 
     def __init__(self, pkg_file):
         super(_ZipPkgReader, self).__init__()
-        self._zipf = ZipFile(pkg_file, "r")
+        try:
+            self._zipf = ZipFile(pkg_file, "r")
+        except BadZipFile:
+            raise PackageNotFoundError(
+                "Package not found or not a valid OPC package file"
+            )
 
     def blob_for(self, pack_uri):
         """Return blob corresponding to `pack_uri`.
diff --git a/tests/opc/test_phys_pkg.py b/tests/opc/test_phys_pkg.py
index 6de0d868b..f02b10f78 100644
--- a/tests/opc/test_phys_pkg.py
+++ b/tests/opc/test_phys_pkg.py
@@ -68,6 +68,10 @@ def it_raises_when_pkg_path_is_not_a_package(self):
         with pytest.raises(PackageNotFoundError):
             PhysPkgReader("foobar")
 
+    def it_raises_when_pkg_stream_is_not_a_zip(self):
+        with pytest.raises(PackageNotFoundError):
+            PhysPkgReader(io.BytesIO(b"not a zip"))
+
 
 class DescribeZipPkgReader:
     def it_is_used_by_PhysPkgReader_when_pkg_is_a_zip(self):