diff --git a/src/pdl/pdl_ast_utils.py b/src/pdl/pdl_ast_utils.py
index a75983c7b..4df30d67f 100644
--- a/src/pdl/pdl_ast_utils.py
+++ b/src/pdl/pdl_ast_utils.py
@@ -126,13 +126,9 @@ def f_expr(self, expr: ExpressionType) -> ExpressionType:
 
 def map_block_children(f: MappedFunctions, block: BlockType) -> BlockType:
     if not isinstance(block, Block):
-        return f.f_block(block)
+        return block
     defs = {x: f.f_block(b) for x, b in block.defs.items()}
-    if block.fallback is not None:
-        fallback = f.f_block(block.fallback)
-    else:
-        fallback = None
-    block = block.model_copy(update={"defs": defs, "fallback": fallback})
+    block = block.model_copy(update={"defs": defs})
     match block:
         case FunctionBlock():
             block.returns = f.f_block(block.returns)
@@ -211,4 +207,6 @@ def map_block_children(f: MappedFunctions, block: BlockType) -> BlockType:
             pass
         case PdlParser():
             block.parser.pdl = f.f_block(block.parser.pdl)
+    if block.fallback is not None:
+        block.fallback = f.f_block(block.fallback)
     return block
diff --git a/tests/test_ast_utils.py b/tests/test_ast_utils.py
new file mode 100644
index 000000000..36b6b1796
--- /dev/null
+++ b/tests/test_ast_utils.py
@@ -0,0 +1,49 @@
+import pathlib
+
+from pdl.pdl_ast_utils import MappedFunctions, iter_block_children, map_block_children
+from pdl.pdl_parser import PDLParseError, parse_file
+
+
+class Counter:
+    def __init__(self):
+        self.cpt = 0
+
+    def incr(self, *args):
+        self.cpt += 1
+
+
+class IterCounter:
+    def __init__(self):
+        self.cpt = 0
+
+    def count(self, ast):
+        self.cpt += 1
+        iter_block_children(self.count, ast)
+
+
+class MapCounter:
+    def __init__(self):
+        self.cpt = 0
+
+    def count(map_self, ast):  # pylint: disable=no-self-argument
+        map_self.cpt += 1
+
+        class C(MappedFunctions):
+            def f_block(_, block):  # pylint: disable=no-self-argument
+                return map_self.count(block)
+
+        _ = map_block_children(C(), ast)
+        return ast
+
+
+def test_ast_iterators() -> None:
+    for yaml_file_name in pathlib.Path(".").glob("**/*.pdl"):
+        try:
+            ast, _ = parse_file(yaml_file_name)
+            iter_cpt = IterCounter()
+            iter_cpt.count(ast.root)
+            map_cpt = MapCounter()
+            map_cpt.count(ast.root)
+            assert iter_cpt.cpt == map_cpt.cpt, yaml_file_name
+        except PDLParseError:
+            pass