diff --git a/Tests/test_file_container.py b/Tests/test_file_container.py
index 2f931fb68..6abf5cc14 100644
--- a/Tests/test_file_container.py
+++ b/Tests/test_file_container.py
@@ -19,7 +19,7 @@ class TestFileContainer(PillowTestCase):
     def test_seek_mode_0(self):
         # Arrange
         mode = 0
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -32,7 +32,7 @@ class TestFileContainer(PillowTestCase):
     def test_seek_mode_1(self):
         # Arrange
         mode = 1
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -45,7 +45,7 @@ class TestFileContainer(PillowTestCase):
     def test_seek_mode_2(self):
         # Arrange
         mode = 2
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -57,7 +57,7 @@ class TestFileContainer(PillowTestCase):
 
     def test_read_n0(self):
         # Arrange
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -65,11 +65,11 @@ class TestFileContainer(PillowTestCase):
             data = container.read()
 
             # Assert
-            self.assertEqual(data, "7\nThis is line 8\n")
+            self.assertEqual(data, b"7\nThis is line 8\n")
 
     def test_read_n(self):
         # Arrange
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -77,11 +77,11 @@ class TestFileContainer(PillowTestCase):
             data = container.read(3)
 
             # Assert
-            self.assertEqual(data, "7\nT")
+            self.assertEqual(data, b"7\nT")
 
     def test_read_eof(self):
         # Arrange
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 22, 100)
 
             # Act
@@ -89,32 +89,32 @@ class TestFileContainer(PillowTestCase):
             data = container.read()
 
             # Assert
-            self.assertEqual(data, "")
+            self.assertEqual(data, b"")
 
     def test_readline(self):
         # Arrange
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 0, 120)
 
             # Act
             data = container.readline()
 
             # Assert
-            self.assertEqual(data, "This is line 1\n")
+            self.assertEqual(data, b"This is line 1\n")
 
     def test_readlines(self):
         # Arrange
         expected = [
-            "This is line 1\n",
-            "This is line 2\n",
-            "This is line 3\n",
-            "This is line 4\n",
-            "This is line 5\n",
-            "This is line 6\n",
-            "This is line 7\n",
-            "This is line 8\n",
+            b"This is line 1\n",
+            b"This is line 2\n",
+            b"This is line 3\n",
+            b"This is line 4\n",
+            b"This is line 5\n",
+            b"This is line 6\n",
+            b"This is line 7\n",
+            b"This is line 8\n",
         ]
-        with open(TEST_FILE) as fh:
+        with open(TEST_FILE, "rb") as fh:
             container = ContainerIO.ContainerIO(fh, 0, 120)
 
             # Act
diff --git a/docs/handbook/tutorial.rst b/docs/handbook/tutorial.rst
index e5da549c3..b5f3b4e96 100644
--- a/docs/handbook/tutorial.rst
+++ b/docs/handbook/tutorial.rst
@@ -468,17 +468,17 @@ Reading from an open file
     with open("hopper.ppm", "rb") as fp:
         im = Image.open(fp)
 
-To read an image from string data, use the :py:class:`~StringIO.StringIO`
-class:
+To read an image from bytes data, use the :py:class:`io.BytesIO` class:
 
-Reading from a string
-^^^^^^^^^^^^^^^^^^^^^
+Reading from a byte string
+^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 ::
 
+    import io
     from PIL import Image
-    import StringIO
-    im = Image.open(StringIO.StringIO(buffer))
+
+    im = Image.open(io.BytesIO(buffer))
 
 Note that the library rewinds the file (using ``seek(0)``) before reading the
 image header. In addition, seek will also be used when the image data is read
diff --git a/src/PIL/ContainerIO.py b/src/PIL/ContainerIO.py
index 3cf9d82d2..b8a3d0582 100644
--- a/src/PIL/ContainerIO.py
+++ b/src/PIL/ContainerIO.py
@@ -82,7 +82,7 @@ class ContainerIO(object):
         else:
             n = self.length - self.pos
         if not n:  # EOF
-            return ""
+            return b""
         self.pos = self.pos + n
         return self.fh.read(n)
 
@@ -92,13 +92,13 @@ class ContainerIO(object):
 
         :returns: An 8-bit string.
         """
-        s = ""
+        s = b""
         while True:
             c = self.read(1)
             if not c:
                 break
             s = s + c
-            if c == "\n":
+            if c == b"\n":
                 break
         return s