diff --git a/shared-module/dotenv/__init__.c b/shared-module/dotenv/__init__.c
index 24587247f0..be8f2353de 100644
--- a/shared-module/dotenv/__init__.c
+++ b/shared-module/dotenv/__init__.c
@@ -124,7 +124,7 @@ STATIC bool key_matches(file_arg *active_file, const char *key) {
             // Still on tentative key; see if it matches the next supplied key character,
             // but don't run off the end of the supplied key.
             if (key_pos < key_len) {
-                matches = matches && key[key_pos] == character;
+                matches = matches && (unsigned char)key[key_pos] == character;
                 escaped = false;
                 key_pos++;
             } else {
diff --git a/tests/circuitpython/dotenv_test.env b/tests/circuitpython/dotenv_test.env
index 7119774fa1..e3bc23d6ce 100644
--- a/tests/circuitpython/dotenv_test.env
+++ b/tests/circuitpython/dotenv_test.env
@@ -21,3 +21,5 @@ space_after_key =value
 space_after_key_before_value = value
 quoted_then_comment='value'#comment
 hash_with_spaces=#value value
+aa🐍bb=key with emoji
+value_with_emoji=aa🐍bb
diff --git a/tests/circuitpython/dotenv_test.py b/tests/circuitpython/dotenv_test.py
index 8445b98030..f217b72dbe 100644
--- a/tests/circuitpython/dotenv_test.py
+++ b/tests/circuitpython/dotenv_test.py
@@ -23,3 +23,5 @@ print(f"space_after_key={dotenv.get_key(FILE, 'space_after_key')}")
 print(f"space_after_key_before_value={dotenv.get_key(FILE, 'space_after_key_before_value')}")
 print(f"quoted_then_comment={dotenv.get_key(FILE, 'quoted_then_comment')}")
 print(f"hash_with_spaces={dotenv.get_key(FILE, 'hash_with_spaces')}")
+print(f"aa🐍bb={dotenv.get_key(FILE, 'aa🐍bb')}")
+print(f"value_with_emoji={dotenv.get_key(FILE, 'value_with_emoji')}")
diff --git a/tests/circuitpython/dotenv_test.py.exp b/tests/circuitpython/dotenv_test.py.exp
index d1cde70182..d67d570999 100644
--- a/tests/circuitpython/dotenv_test.py.exp
+++ b/tests/circuitpython/dotenv_test.py.exp
@@ -19,3 +19,5 @@ space_after_key=value
 space_after_key_before_value=value
 quoted_then_comment=value
 hash_with_spaces=#value value
+aa🐍bb=key with emoji
+value_with_emoji=aa🐍bb