diff --git a/operator-context.go b/operator-context.go
index 4ee4685..20b1e1d 100644
--- a/operator-context.go
+++ b/operator-context.go
@@ -31,16 +31,20 @@ func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	if sourceCtx != nil {
-		keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
-		d := make(map[string]any)
-		for _, key := range keys {
-			d[key], _ = sourceCtx.GetVar(key)
+		if formatter, ok := ctx.(Formatter); ok {
+			v = formatter.ToString(0)
+		} else {
+			keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+			d := make(map[string]any)
+			for _, key := range keys {
+				d[key], _ = sourceCtx.GetVar(key)
+			}
+			keys = sourceCtx.EnumFuncs(func(name string) bool { return true })
+			for _, key := range keys {
+				d[key], _ = sourceCtx.GetFuncInfo(key)
+			}
+			v = d
 		}
-		keys = sourceCtx.EnumFuncs(func(name string) bool { return true })
-		for _, key := range keys {
-			d[key], _ =sourceCtx.GetFuncInfo(key)
-		}
-		v = d
 	} else {
 		err = self.errIncompatibleType(childValue)
 	}