diff --git a/src/NUnitEngine/nunit.engine.core/Internal/RuntimeFrameworks/NetCoreFrameworkLocator.cs b/src/NUnitEngine/nunit.engine.core/Internal/RuntimeFrameworks/NetCoreFrameworkLocator.cs
index 71eff1cf6..420dd4a6a 100644
--- a/src/NUnitEngine/nunit.engine.core/Internal/RuntimeFrameworks/NetCoreFrameworkLocator.cs
+++ b/src/NUnitEngine/nunit.engine.core/Internal/RuntimeFrameworks/NetCoreFrameworkLocator.cs
@@ -12,6 +12,8 @@ namespace NUnit.Engine.Internal.RuntimeFrameworks
 {
     internal static class NetCoreFrameworkLocator
     {
+        static Logger log = InternalTrace.GetLogger(typeof(NetCoreFrameworkLocator));
+
         public static IEnumerable<RuntimeFramework> FindDotNetCoreFrameworks()
         {
             List<Version> alreadyFound = new List<Version>();
@@ -22,7 +24,12 @@ public static IEnumerable<RuntimeFramework> FindDotNetCoreFrameworks()
                 if (TryGetVersionFromString(dirName, out newVersion) && !alreadyFound.Contains(newVersion))
                 {
                     alreadyFound.Add(newVersion);
-                    yield return new RuntimeFramework(RuntimeType.NetCore, newVersion);
+                    // HACK: Avoid Exception for an unknown version - see issue #1223
+                    // Requires change in RuntimeFramework.GetClrVersionForFramework()
+                    if (newVersion.Major <= 7)
+                        yield return new RuntimeFramework(RuntimeType.NetCore, newVersion);
+                    else
+                        log.Error($"Found .NET {newVersion.ToString(2)}, which is not yet supported.");
                 }
             }
 
diff --git a/src/NUnitEngine/nunit.engine.core/RuntimeFramework.cs b/src/NUnitEngine/nunit.engine.core/RuntimeFramework.cs
index 569f6b930..42782f462 100644
--- a/src/NUnitEngine/nunit.engine.core/RuntimeFramework.cs
+++ b/src/NUnitEngine/nunit.engine.core/RuntimeFramework.cs
@@ -134,6 +134,7 @@ public RuntimeFramework(RuntimeType runtime, Version version, string profile)
             // Version 0.0 means any version so we can't deduce anything
             if (version != DefaultVersion)
             {
+                Debug.Assert(IsFrameworkVersion(version));
                 if (IsFrameworkVersion(version))
                     ClrVersion = GetClrVersionForFramework(version);
                 else
diff --git a/src/NUnitEngine/nunit.engine/Services/RuntimeFrameworkService.cs b/src/NUnitEngine/nunit.engine/Services/RuntimeFrameworkService.cs
index bd5cecf99..5347ec49d 100644
--- a/src/NUnitEngine/nunit.engine/Services/RuntimeFrameworkService.cs
+++ b/src/NUnitEngine/nunit.engine/Services/RuntimeFrameworkService.cs
@@ -173,27 +173,6 @@ private RuntimeFramework SelectRuntimeFrameworkInner(TestPackage package)
             return targetFramework;
         }
 
-
-        /// <summary>
-        /// Returns the best available framework that matches a target framework.
-        /// If the target framework has a build number specified, then an exact
-        /// match is needed. Otherwise, the matching framework with the highest
-        /// build number is used.
-        /// </summary>
-        public RuntimeFramework GetBestAvailableFramework(RuntimeFramework target)
-        {
-            RuntimeFramework result = target;
-
-            foreach (RuntimeFramework framework in _availableRuntimes)
-                if (framework.Supports(target))
-                {
-                    if (framework.ClrVersion.Build > result.ClrVersion.Build)
-                        result = framework;
-                }
-
-            return result;
-        }
-
         /// <summary>
         /// Use Mono.Cecil to get information about all assemblies and
         /// apply it to the package using special internal keywords.