diff --git a/hg b/hg
--- a/hg
+++ b/hg
@@ -11,13 +11,6 @@
 import os
 import sys
 
-if os.environ.get('HGUNICODEPEDANTRY', False):
-    try:
-        reload(sys)
-        sys.setdefaultencoding("undefined")
-    except NameError:
-        pass
-
 libdir = '@LIBDIR@'
 
 if libdir != '@' 'LIBDIR' '@':
diff --git a/rust/hgcli/src/main.rs b/rust/hgcli/src/main.rs
--- a/rust/hgcli/src/main.rs
+++ b/rust/hgcli/src/main.rs
@@ -104,19 +104,6 @@
     }
 }
 
-fn update_encoding(_py: Python, _sys_mod: &PyModule) {
-    // Call sys.setdefaultencoding("undefined") if HGUNICODEPEDANTRY is set.
-    let pedantry = env::var("HGUNICODEPEDANTRY").is_ok();
-
-    if pedantry {
-        // site.py removes the sys.setdefaultencoding attribute. So we need
-        // to reload the module to get a handle on it. This is a lesser
-        // used feature and we'll support this later.
-        // TODO support this
-        panic!("HGUNICODEPEDANTRY is not yet supported");
-    }
-}
-
 fn update_modules_path(env: &Environment, py: Python, sys_mod: &PyModule) {
     let sys_path = sys_mod.get(py, "path").unwrap();
     sys_path
@@ -210,7 +197,6 @@
 fn run_py(env: &Environment, py: Python) -> PyResult<()> {
     let sys_mod = py.import("sys").unwrap();
 
-    update_encoding(py, &sys_mod);
     update_modules_path(&env, py, &sys_mod);
 
     // TODO consider a better error message on failure to import.
diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -80,13 +80,6 @@
     import pipes
     shellquote = pipes.quote
 
-if os.environ.get('RTUNICODEPEDANTRY', False):
-    try:
-        reload(sys)
-        sys.setdefaultencoding("undefined")
-    except NameError:
-        pass
-
 processlock = threading.Lock()
 
 pygmentspresent = False