Unable to access custom editor namespace from runtime assembly

Hi guys

I have a utility class in the editor assembly:

 namespace Hydra.HydraCommon.Editor.Utils
 {
     public static class ScriptableObjectUtils {}
 }

And I'm trying to access it via the runtime assembly:

 #if UNITY_EDITOR
 
 Hydra.HydraCommon.Editor.Utils.ScriptableObjectUtils.DoSomething();
 
 #endif

However the compiler tells me that the "Editor" namespace does not exist in "HydraCommon".

I know for a fact I can execute editor code in the runtime assembly via something like:

 #if UNITY_EDITOR
 
 UnityEditor.Whatever...;
 
 #endif

Why can I not do the same with namespaced classes in the editor assembly?

Thanks, Ves