diff --git a/src/Seq.Api/Model/Signals/SignalExpressionPart.cs b/src/Seq.Api/Model/Signals/SignalExpressionPart.cs
index c0615e3..c5bda8f 100644
--- a/src/Seq.Api/Model/Signals/SignalExpressionPart.cs
+++ b/src/Seq.Api/Model/Signals/SignalExpressionPart.cs
@@ -74,7 +74,7 @@ public override string ToString()
                 return $"{Group(Left)},{Group(Right)}";
 
             if (Kind == SignalExpressionKind.Union)
-                return $"{Group(Left)}+{Group(Right)}";
+                return $"{Group(Left)}~{Group(Right)}";
 
             throw new InvalidOperationException("Invalid signal expression kind.");
         }
diff --git a/src/Seq.Api/Seq.Api.csproj b/src/Seq.Api/Seq.Api.csproj
index c8f5e03..0b4a849 100644
--- a/src/Seq.Api/Seq.Api.csproj
+++ b/src/Seq.Api/Seq.Api.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>Client library for the Seq HTTP API.</Description>
-    <VersionPrefix>4.2.1</VersionPrefix>
+    <VersionPrefix>4.2.2</VersionPrefix>
     <Authors>Datalust;Contributors</Authors>
     <TargetFrameworks>netstandard1.3;net452</TargetFrameworks>
     <NoWarn>$(NoWarn);CS1591</NoWarn>