diff --git a/ibis/expr/types/arrays.py b/ibis/expr/types/arrays.py
index 6518b5372827..add931bfeb2d 100644
--- a/ibis/expr/types/arrays.py
+++ b/ibis/expr/types/arrays.py
@@ -444,7 +444,7 @@ def map(self, func: Deferred | Callable[[ir.Value], ir.Value]) -> ir.ArrayValue:
         └────────────────────────┘
         """
         if isinstance(func, Deferred):
-            name = str(func)
+            name = "_"
         else:
             name = next(iter(inspect.signature(func).parameters.keys()))
         parameter = ops.Argument(
@@ -544,7 +544,7 @@ def filter(
         └───────────────────────────────┘
         """
         if isinstance(predicate, Deferred):
-            name = str(predicate)
+            name = "_"
         else:
             name = next(iter(inspect.signature(predicate).parameters.keys()))
         parameter = ops.Argument(