diff --git a/testing/cffi0/backend_tests.py b/testing/cffi0/backend_tests.py
index 7b55ba8..7008f82 100644
--- a/testing/cffi0/backend_tests.py
+++ b/testing/cffi0/backend_tests.py
@@ -1241,7 +1241,7 @@ class BackendTests:
             py.test.skip(str(e))
         f.write(ffi.buffer(a, 1000 * ffi.sizeof("int")))
         f.seek(0)
-        assert f.read() == array.array('i', range(1000)).tostring()
+        assert f.read() == array.array('i', range(1000)).tobytes()
         f.seek(0)
         b = ffi.new("int[]", 1005)
         f.readinto(ffi.buffer(b, 1000 * ffi.sizeof("int")))
@@ -1260,7 +1260,7 @@ class BackendTests:
             py.test.skip(str(e))
         f.write(ffi.buffer(a, 1000 * ffi.sizeof("int")))
         f.seek(0)
-        assert f.read() == array.array('i', range(1000)).tostring()
+        assert f.read() == array.array('i', range(1000)).tobytes()
         f.seek(0)
         b = ffi.new("int[]", 1005)
         f.readinto(ffi.buffer(b, 1000 * ffi.sizeof("int")))
diff --git a/testing/cffi1/test_new_ffi_1.py b/testing/cffi1/test_new_ffi_1.py
index d6eeecd..5b36c50 100644
--- a/testing/cffi1/test_new_ffi_1.py
+++ b/testing/cffi1/test_new_ffi_1.py
@@ -1220,7 +1220,7 @@ class TestNewFFI1:
             py.test.skip(str(e))
         f.write(ffi.buffer(a, 1000 * ffi.sizeof("int")))
         f.seek(0)
-        assert f.read() == array.array('i', range(1000)).tostring()
+        assert f.read() == array.array('i', range(1000)).tobytes()
         f.seek(0)
         b = ffi.new("int[]", 1005)
         f.readinto(ffi.buffer(b, 1000 * ffi.sizeof("int")))
@@ -1238,7 +1238,7 @@ class TestNewFFI1:
             py.test.skip(str(e))
         f.write(ffi.buffer(a, 1000 * ffi.sizeof("int")))
         f.seek(0)
-        assert f.read() == array.array('i', range(1000)).tostring()
+        assert f.read() == array.array('i', range(1000)).tobytes()
         f.seek(0)
         b = ffi.new("int[]", 1005)
         f.readinto(ffi.buffer(b, 1000 * ffi.sizeof("int")))