diff --git a/src/uproot/streamers.py b/src/uproot/streamers.py
index 066363b0a..4a4b7000d 100644
--- a/src/uproot/streamers.py
+++ b/src/uproot/streamers.py
@@ -999,14 +999,14 @@ def class_code(
                 else:
                     # AwkwardForth testing E: test_0637's 01,02,05,08,09,11,12,13,15,16,29,35,39,45,46,47,49,50,56
                     read_members.append("        if forth_obj is not None:")
-                    for i in range(len(formats[0])):
+                    for i in range(len(formats[-1])):
                         read_members.extend(
                             [
                                 "           key = key_number ; key_number += 1",
                                 '           form_key = f"node{key}-data"',
-                                f'           nested_forth_stash = af.Node(f"node{{key}}", field_name={fields[0][i]!r}, form_details={{ "class": "NumpyArray", "primitive": "{af.struct_to_dtype_name[formats[0][i]]}", "inner_shape": [], "parameters": {{}}, "form_key": f"node{{key}}"}})',
-                                f'           nested_forth_stash.header_code.append(f"output {{form_key}} {af.struct_to_dtype_name[formats[0][i]]}\\n")',
-                                f'           nested_forth_stash.pre_code.append(f"stream !{formats[0][i]}-> {{form_key}}\\n")',
+                                f'           nested_forth_stash = af.Node(f"node{{key}}", field_name={fields[-1][i]!r}, form_details={{ "class": "NumpyArray", "primitive": "{af.struct_to_dtype_name[formats[-1][i]]}", "inner_shape": [], "parameters": {{}}, "form_key": f"node{{key}}"}})',
+                                f'           nested_forth_stash.header_code.append(f"output {{form_key}} {af.struct_to_dtype_name[formats[-1][i]]}\\n")',
+                                f'           nested_forth_stash.pre_code.append(f"stream !{formats[-1][i]}-> {{form_key}}\\n")',
                                 "           forth_obj.add_node(nested_forth_stash)",
                             ]
                         )
diff --git a/tests/test_1221_AwkwardForth_bug.py b/tests/test_1221_AwkwardForth_bug.py
new file mode 100644
index 000000000..f9d2ca350
--- /dev/null
+++ b/tests/test_1221_AwkwardForth_bug.py
@@ -0,0 +1,22 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot5/blob/main/LICENSE
+
+import pytest
+import uproot
+import skhep_testdata
+
+
+def test():
+    with uproot.open(skhep_testdata.data_path("uproot-issue-1221.root")) as file:
+        record = file["TrkAna"]["trkana"]["demtsh"].array()[-1, -1, -1]
+        assert record.tolist() == {
+            "wdot": -0.6311486959457397,
+            "dhit": True,
+            "poca": {
+                "fCoordinates": {
+                    "fX": -526.5504760742188,
+                    "fY": -195.0541534423828,
+                    "fZ": 1338.90771484375,
+                }
+            },
+            "dactive": True,
+        }