diff --git a/aeneas/diagnostics.py b/aeneas/diagnostics.py
index 7d9e98a1..6f4e291f 100644
--- a/aeneas/diagnostics.py
+++ b/aeneas/diagnostics.py
@@ -56,9 +56,9 @@ def check_shell_encoding(cls):
         """
         is_in_utf8 = True
         is_out_utf8 = True
-        if sys.stdin.encoding not in ["UTF-8", "UTF8"]:
+        if sys.stdin.encoding not in ["UTF-8", "UTF8", "utf-8", "utf8"]:
             is_in_utf8 = False
-        if sys.stdout.encoding not in ["UTF-8", "UTF8"]:
+        if sys.stdout.encoding not in ["UTF-8", "UTF8", "utf-8", "utf8"]:
             is_out_utf8 = False
         if (is_in_utf8) and (is_out_utf8):
             gf.print_success(u"shell encoding OK")
diff --git a/aeneas/tools/abstract_cli_program.py b/aeneas/tools/abstract_cli_program.py
index be5bb2fa..b5b9fadd 100644
--- a/aeneas/tools/abstract_cli_program.py
+++ b/aeneas/tools/abstract_cli_program.py
@@ -295,10 +295,10 @@ def run(self, arguments, show_help=True):
         if self.use_sys:
             # check that sys.stdin.encoding and sys.stdout.encoding are set to utf-8
             if not gf.FROZEN:
-                if sys.stdin.encoding not in ["UTF-8", "UTF8"]:
+                if sys.stdin.encoding not in ["UTF-8", "UTF8", "utf-8", "utf8"]:
                     self.print_warning(u"The default input encoding is not UTF-8.")
                     self.print_warning(u"You might want to set 'PYTHONIOENCODING=UTF-8' in your shell.")
-                if sys.stdout.encoding not in ["UTF-8", "UTF8"]:
+                if sys.stdout.encoding not in ["UTF-8", "UTF8", "utf-8", "utf8"]:
                     self.print_warning(u"The default output encoding is not UTF-8.")
                     self.print_warning(u"You might want to set 'PYTHONIOENCODING=UTF-8' in your shell.")
             # decode using sys.stdin.encoding