diff --git a/src/Sqids/SqidsEncoder.cs b/src/Sqids/SqidsEncoder.cs
index 8cab01f..5fe3f19 100644
--- a/src/Sqids/SqidsEncoder.cs
+++ b/src/Sqids/SqidsEncoder.cs
@@ -81,6 +81,12 @@ public SqidsEncoder(SqidsOptions options)
 				$"The alphabet must contain at least {MinAlphabetLength} characters."
 			);
 
+		if (Encoding.UTF8.GetByteCount(options.Alphabet) != options.Alphabet.Length)
+			throw new ArgumentOutOfRangeException(
+				nameof(options.MinLength),
+				$"The alphabet must not contain multi-byte characters."
+			);
+
 		if (options.MinLength < 0 || options.MinLength > MaxMinLength)
 			throw new ArgumentOutOfRangeException(
 				nameof(options.MinLength),
diff --git a/test/Sqids.Tests/AlphabetTests.cs b/test/Sqids.Tests/AlphabetTests.cs
index c611e5e..31ab9b3 100644
--- a/test/Sqids.Tests/AlphabetTests.cs
+++ b/test/Sqids.Tests/AlphabetTests.cs
@@ -39,6 +39,7 @@ int[] numbers
 
 	[TestCase("aabcdefg")] // NOTE: Repeated characters
 	[TestCase("ab")] // NOTE: Too short
+	[TestCase("ë1092")] // NOTE: Contains a multi-byte character
 	public void Instantiate_WithInvalidAlphabet_Throws(string invalidAlphabet)
 	{
 #if NET7_0_OR_GREATER