diff --git a/Source/Core/AST/Absy.cs b/Source/Core/AST/Absy.cs
index 8747597ab..f169ace39 100644
--- a/Source/Core/AST/Absy.cs
+++ b/Source/Core/AST/Absy.cs
@@ -2974,9 +2974,13 @@ public override void Resolve(ResolutionContext rc)
       if (RefinedAction != null)
       {
         RefinedAction.Resolve(rc);
+        if (!HasMoverType)
+        {
+          MoverType = MoverType.Atomic;
+        }
         if (RefinedAction.ActionDecl is { HasMoverType: false })
         {
-          rc.Error(this, $"refined action {RefinedAction.ActionDecl.Name} must have a mover type");
+          RefinedAction.ActionDecl.MoverType = MoverType.Atomic;
         }
       }
       if (InvariantAction != null)
@@ -3298,7 +3302,7 @@ public override void Resolve(ResolutionContext rc)
         RefinedAction.Resolve(rc);
         if (RefinedAction.ActionDecl is { HasMoverType: false })
         {
-          rc.Error(this, $"refined action {RefinedAction.ActionDecl.Name} must have a mover type");
+          RefinedAction.ActionDecl.MoverType = MoverType.Atomic;
         }
       }
 
diff --git a/Source/Core/BoogiePL.atg b/Source/Core/BoogiePL.atg
index 6f1f0c676..6d336e458 100644
--- a/Source/Core/BoogiePL.atg
+++ b/Source/Core/BoogiePL.atg
@@ -705,16 +705,16 @@ ActionDecl<bool isPure, out ActionDecl actionDecl, out Implementation impl, out
        }
      }
      if (isAsync) {
-       if (moverType == MoverType.None)
-       {
-         this.SemErr("async action must have a mover type");
-       }
-       else if (outs.Count > 0)
+       if (outs.Count > 0)
        {
          this.SemErr("async action must not have output parameters");
        }
        else
        {
+         if (moverType == MoverType.None)
+         {
+           moverType = MoverType.Atomic;
+         }
          datatypeTypeCtorDecl = new DatatypeTypeCtorDecl(name, name.val, new List<TypeVariable>(), null);
          var fields = ins.Select(v => new Formal(v.tok, new TypedIdent(v.TypedIdent.tok, v.Name, v.TypedIdent.Type), true, v.Attributes)).ToList<Variable>();
          datatypeTypeCtorDecl.AddConstructor(name, name.val, fields);
diff --git a/Source/Core/Parser.cs b/Source/Core/Parser.cs
index 871576e28..09a9b05ba 100644
--- a/Source/Core/Parser.cs
+++ b/Source/Core/Parser.cs
@@ -725,16 +725,16 @@ void ActionDecl(bool isPure, out ActionDecl actionDecl, out Implementation impl,
 		 }
 		}
 		if (isAsync) {
-		 if (moverType == MoverType.None)
-		 {
-		   this.SemErr("async action must have a mover type");
-		 }
-		 else if (outs.Count > 0)
+		 if (outs.Count > 0)
 		 {
 		   this.SemErr("async action must not have output parameters");
 		 }
 		 else
 		 {
+		   if (moverType == MoverType.None)
+		   {
+		     moverType = MoverType.Atomic;
+		   }
 		   datatypeTypeCtorDecl = new DatatypeTypeCtorDecl(name, name.val, new List<TypeVariable>(), null);
 		   var fields = ins.Select(v => new Formal(v.tok, new TypedIdent(v.TypedIdent.tok, v.Name, v.TypedIdent.Type), true, v.Attributes)).ToList<Variable>();
 		   datatypeTypeCtorDecl.AddConstructor(name, name.val, fields);