diff --git a/SimpleOTP.Test/OTPServiceUnitTest.cs b/SimpleOTP.Test/OTPServiceUnitTest.cs
index a5238bd..36b7be2 100644
--- a/SimpleOTP.Test/OTPServiceUnitTest.cs
+++ b/SimpleOTP.Test/OTPServiceUnitTest.cs
@@ -41,6 +41,31 @@ namespace SimpleOTP.Test
 			Assert.AreEqual(293657, code.Code);
 		}
 
+		/// <summary>
+		/// Test time-based OTP generator with customly formatted secret.
+		/// </summary>
+		[TestMethod("Secret format test")]
+		public void FormatTest()
+		{
+			Console.Write("Uppercase space-separated: ");
+			var config = totpConfig with { Secret = "JBSW Y3DP EHPK 3PXP" };
+			var code = OTPService.GenerateCode(ref config, time);
+			Assert.AreEqual(160102, code.Code);
+			Console.WriteLine("Passed.");
+
+			Console.Write("Lowercase space-separated: ");
+			config = totpConfig with { Secret = "jbsw y3dp ehpk 3pxp" };
+			code = OTPService.GenerateCode(ref config, time);
+			Assert.AreEqual(160102, code.Code);
+			Console.WriteLine("Passed.");
+
+			Console.Write("Lowercase: ");
+			config = totpConfig with { Secret = "jbswy3dpehpk3pxp" };
+			code = OTPService.GenerateCode(ref config, time);
+			Assert.AreEqual(160102, code.Code);
+			Console.WriteLine("Passed.");
+		}
+
 		/// <summary>
 		/// Test HOTP generator with pre-calculated code.
 		/// </summary>
diff --git a/SimpleOTP/OTPService.cs b/SimpleOTP/OTPService.cs
index 789909e..fbc1154 100644
--- a/SimpleOTP/OTPService.cs
+++ b/SimpleOTP/OTPService.cs
@@ -48,7 +48,7 @@ namespace SimpleOTP
 		/// </returns>
 		public static OTPCode GenerateCode(ref OTPConfiguration target, DateTime date)
 		{
-			byte[] keyBytes = Base32Encoder.Decode(target.Secret);
+			byte[] keyBytes = Base32Encoder.Decode(target.Secret.ToUpperInvariant().Replace(" ", string.Empty));
 			long counter = target.Type == OTPType.HOTP ? target.Counter : GetCurrentCounter(date.ToUniversalTime(), (int)target.Period.TotalSeconds);
 			byte[] counterBytes = BitConverter.GetBytes(counter);
 
diff --git a/SimpleOTP/SimpleOTP.csproj b/SimpleOTP/SimpleOTP.csproj
index 93f655d..7c3b95f 100644
--- a/SimpleOTP/SimpleOTP.csproj
+++ b/SimpleOTP/SimpleOTP.csproj
@@ -12,7 +12,7 @@
 	<PropertyGroup>
 		<PackageId>SimpleOTP</PackageId>
 		<AssemblyName>SimpleOTP</AssemblyName>
-		<Version>1.2.2</Version>
+		<Version>1.2.3</Version>
 		<Description>.NET library for TOTP/HOTP implementation on server (ASP.NET) or client (Xamarin) side</Description>
 		<Authors>Eugene Fox</Authors>
 		<Company>FoxDev Studio</Company>
@@ -22,8 +22,7 @@
 		<RepositoryUrl>https://github.com/XFox111/SimpleOTP</RepositoryUrl>
 		<NeutralLanguage>en-US</NeutralLanguage>
 		<PackageTags>otp;totp;dotnet;hotp;authenticator;2fa;mfa;security;oath</PackageTags>
-		<PackageReleaseNotes>- Fixed Base32 encoder
-- Updated NuGet dependency packages</PackageReleaseNotes>
+		<PackageReleaseNotes>- Fixed invalid code generation with secrets which are lowercase or space-separated</PackageReleaseNotes>
 	</PropertyGroup>
 
 	<PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">