diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 73b57b2..4719773 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -2228,15 +2228,9 @@
             env = os.environ.copy()
             env[key] = value
             # Use C locale to get ASCII for the locale encoding to force
-            # surrogate-escaping of \xFF in the child process; otherwise it can
-            # be decoded as-is if the default locale is latin-1.
+            # surrogate-escaping of \xFF in the child process
             env['LC_ALL'] = 'C'
-            if sys.platform.startswith("aix"):
-                # On AIX, the C locale uses the Latin1 encoding
-                decoded_value = encoded_value.decode("latin1", "surrogateescape")
-            else:
-                # On other UNIXes, the C locale uses the ASCII encoding
-                decoded_value = value
+            decoded_value = value
             stdout = subprocess.check_output(
                 [sys.executable, "-c", script],
                 env=env)
diff --git a/Misc/NEWS.d/next/Tests/2018-08-26-13-12-34.bpo-11193.H8fCGa.rst b/Misc/NEWS.d/next/Tests/2018-08-26-13-12-34.bpo-11193.H8fCGa.rst
new file mode 100644
index 0000000..b31caa6
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2018-08-26-13-12-34.bpo-11193.H8fCGa.rst
@@ -0,0 +1 @@
+Remove special condition for AIX in `test_subprocess.test_undecodable_env`