Method not found: 'UnityEngine.AnimatorControllerParameter.set_name'

This shows up in the log in build mode, but doesn't happen when I run from the editor

That same message fills up the log

This is the code:

Code (CSharp):

1. public static class AvatarAnimatorControllerParameters
2.     {
3.         static public readonly UnityEngine.AnimatorControllerParameter Property_TotalSpeedPercentile = new UnityEngine.AnimatorControllerParameter();
4.         static public readonly UnityEngine.AnimatorControllerParameter Property_ForwardBackSpeedPercentile = new UnityEngine.AnimatorControllerParameter();
5.         static public readonly UnityEngine.AnimatorControllerParameter Property_RightLeftSpeedPercentile = new UnityEngine.AnimatorControllerParameter();
6.         static public readonly UnityEngine.AnimatorControllerParameter[] allParameters;
7.  
8.         static AvatarAnimatorControllerParameters()
9.         {
10.             Property_TotalSpeedPercentile.name = "Property_TotalSpeedPercentile";
11.             Property_TotalSpeedPercentile.type = UnityEngine.AnimatorControllerParameterType.Float;
12.  
13.             Property_ForwardBackSpeedPercentile.name = "Property_ForwardBackSpeedPercentile";
14.             Property_ForwardBackSpeedPercentile.type = UnityEngine.AnimatorControllerParameterType.Float;
15.  
16.             Property_RightLeftSpeedPercentile.name = "Property_RightLeftSpeedPercentile";
17.             Property_RightLeftSpeedPercentile.type = UnityEngine.AnimatorControllerParameterType.Float;
18.  
19.             allParameters = new UnityEngine.AnimatorControllerParameter[] { Property_TotalSpeedPercentile, Property_ForwardBackSpeedPercentile, Property_RightLeftSpeedPercentile };
20.         }
21.     }
22.  

 

If I create the AnimatorControllerParameter at runtime I get this instead:
MissingMethodException: Method not found: 'UnityEngine.AnimatorControllerParameter.set_name'.
at BaseMod.V1.AvatarMovementEffects.Update () [0x00000] in <filename unknown>:0

Code (CSharp):

1. static public UnityEngine.AnimatorControllerParameter Property_TotalSpeedPercentile()
2.         {
3.             UnityEngine.AnimatorControllerParameter acp = new UnityEngine.AnimatorControllerParameter();
4.             acp.name = "Property_TotalSpeedPercentile";
5.             acp.type = UnityEngine.AnimatorControllerParameterType.Float;
6.             return acp;
7.         }