diff --git a/Firely.Fhir.Packages.props b/Firely.Fhir.Packages.props
index 3203e27..1940043 100644
--- a/Firely.Fhir.Packages.props
+++ b/Firely.Fhir.Packages.props
@@ -5,13 +5,13 @@
 		<TargetFrameworks>net6.0;netstandard2.0;</TargetFrameworks>
 		<Nullable>enable</Nullable>
 		<GeneratePackageOnBuild>false</GeneratePackageOnBuild>
-		<FhirNetSdkVersion>5.5.0</FhirNetSdkVersion>
+		<FhirNetSdkVersion>5.5.1</FhirNetSdkVersion>
 	</PropertyGroup>
 	
     <!-- Solution-wide properties for NuGet packaging -->
     <PropertyGroup>
         <LangVersion>9.0</LangVersion>
-        <VersionPrefix>5.5.0</VersionPrefix>
+        <VersionPrefix>4.2.1</VersionPrefix>
         <VersionSuffix></VersionSuffix>
         <Authors>Firely</Authors>
         <Company>Firely (https://fire.ly)</Company>