diff --git a/lib/src/charset.dart b/lib/src/charset.dart
index 92d6bd4..6be3564 100644
--- a/lib/src/charset.dart
+++ b/lib/src/charset.dart
@@ -359,6 +359,8 @@ class Charset {
       encoding.encode(char);
     } on FormatException catch (_) {
       return false;
+    } on ArgumentError catch (_) {
+      return false;
     }
     return true;
   }
@@ -369,6 +371,8 @@ class Charset {
       encoding.decode(char);
     } on FormatException catch (_) {
       return false;
+    } on ArgumentError catch (_) {
+      return false;
     }
     return true;
   }