diff --git a/girepository/giroffsets.c b/girepository/giroffsets.c
index 60e6e341f..8a5b95c39 100644
--- a/girepository/giroffsets.c
+++ b/girepository/giroffsets.c
@@ -465,6 +465,8 @@ compute_union_field_offsets (GIIrTypelibBuild *build,
                 {
                   size = MAX (size, member_size);
                   alignment = MAX (alignment, member_alignment);
+                  field->offset = 0;
+                  field->offset_state = GI_IR_OFFSETS_COMPUTED;
                 }
               else
                 have_error = TRUE;
diff --git a/girepository/tests/field-info.c b/girepository/tests/field-info.c
new file mode 100644
index 000000000..ffde8eff4
--- /dev/null
+++ b/girepository/tests/field-info.c
@@ -0,0 +1,168 @@
+/*
+ * Copyright 2025 Philip Chimento <philip.chimento@gmail.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "girepository.h"
+#include "glib.h"
+#include "test-common.h"
+
+static void
+test_basic_struct_field (RepositoryFixture *fx,
+                         const void *unused)
+{
+  GIStructInfo *struct_info = NULL;
+  GIFieldInfo *field_info = NULL;
+  GITypeInfo *type_info = NULL;
+  GIFieldInfoFlags flags;
+
+  g_test_summary ("Test basic properties of a GIFieldInfo from a C struct");
+
+  struct_info = GI_STRUCT_INFO (gi_repository_find_by_name (fx->repository, "GLib", "DebugKey"));
+  g_assert_nonnull (struct_info);
+
+  field_info = gi_struct_info_get_field (struct_info, 0);
+  g_assert_true (GI_IS_FIELD_INFO (field_info));
+  g_assert_cmpstr (gi_base_info_get_name (GI_BASE_INFO (field_info)), ==, "key");
+
+  flags = gi_field_info_get_flags (field_info);
+  g_assert_cmpuint (flags, ==, GI_FIELD_IS_READABLE | GI_FIELD_IS_WRITABLE);
+
+  /* Guaranteed across platforms, because it's the first field */
+  g_assert_cmpuint (gi_field_info_get_offset (field_info), ==, 0);
+
+  type_info = gi_field_info_get_type_info (field_info);
+  g_assert_cmpuint (gi_type_info_get_tag (type_info), ==, GI_TYPE_TAG_UTF8);
+  g_assert_true (gi_type_info_is_pointer (type_info));
+
+  g_clear_pointer (&type_info, gi_base_info_unref);
+  g_clear_pointer (&field_info, gi_base_info_unref);
+  g_clear_pointer (&struct_info, gi_base_info_unref);
+}
+
+static void
+test_basic_union_field (RepositoryFixture *fx,
+                        const void *unused)
+{
+  GIUnionInfo *union_info = NULL;
+  GIFieldInfo *field_info = NULL;
+  GITypeInfo *type_info = NULL;
+  GIFieldInfoFlags flags;
+
+  g_test_summary ("Test basic properties of a GIFieldInfo from a C union");
+
+  union_info = GI_UNION_INFO (gi_repository_find_by_name (fx->repository, "GLib", "DoubleIEEE754"));
+  g_assert_nonnull (union_info);
+
+  field_info = gi_union_info_get_field (union_info, 0);
+  g_assert_true (GI_IS_FIELD_INFO (field_info));
+  g_assert_cmpstr (gi_base_info_get_name (GI_BASE_INFO (field_info)), ==, "v_double");
+
+  flags = gi_field_info_get_flags (field_info);
+  g_assert_cmpuint (flags, ==, GI_FIELD_IS_READABLE | GI_FIELD_IS_WRITABLE);
+
+  /* Guaranteed across platforms, because union offsets are always 0 */
+  g_assert_cmpuint (gi_field_info_get_offset (field_info), ==, 0);
+
+  type_info = gi_field_info_get_type_info (field_info);
+  g_assert_cmpuint (gi_type_info_get_tag (type_info), ==, GI_TYPE_TAG_DOUBLE);
+  g_assert_false (gi_type_info_is_pointer (type_info));
+
+  g_clear_pointer (&type_info, gi_base_info_unref);
+  g_clear_pointer (&field_info, gi_base_info_unref);
+  g_clear_pointer (&union_info, gi_base_info_unref);
+}
+
+static void
+test_read_write_struct_field (RepositoryFixture *fx,
+                              const void *unused)
+{
+  GIStructInfo *struct_info = NULL;
+  GIFieldInfo *field_info = NULL;
+  GDebugKey instance;
+  GIArgument arg;
+  gboolean ok;
+
+  g_test_summary ("Test reading and writing of a GIFieldInfo from a C union");
+
+  struct_info = GI_STRUCT_INFO (gi_repository_find_by_name (fx->repository, "GLib", "DebugKey"));
+  g_assert_nonnull (struct_info);
+
+  field_info = gi_struct_info_get_field (struct_info, 1);
+  g_assert_nonnull (field_info);
+
+  instance.value = 0xfeed;
+  ok = gi_field_info_get_field (field_info, &instance, &arg);
+  g_assert_true (ok);
+  g_assert_cmpuint (arg.v_uint, ==, 0xfeed);
+
+  arg.v_uint = 0x6502;
+  ok = gi_field_info_set_field (field_info, &instance, &arg);
+  g_assert_true (ok);
+  g_assert_cmpuint (instance.value, ==, 0x6502);
+
+  g_clear_pointer (&field_info, gi_base_info_unref);
+  g_clear_pointer (&struct_info, gi_base_info_unref);
+}
+
+static void
+test_read_write_union_field (RepositoryFixture *fx,
+                             const void *unused)
+{
+  GIUnionInfo *union_info = NULL;
+  GIFieldInfo *field_info = NULL;
+  GDoubleIEEE754 instance;
+  GIArgument arg;
+  gboolean ok;
+
+  g_test_summary ("Test reading and writing of a GIFieldInfo from a C union");
+
+  union_info = GI_UNION_INFO (gi_repository_find_by_name (fx->repository, "GLib", "DoubleIEEE754"));
+  g_assert_nonnull (union_info);
+
+  field_info = gi_union_info_get_field (union_info, 0);
+  g_assert_nonnull (field_info);
+
+  instance.v_double = G_PI;
+  ok = gi_field_info_get_field (field_info, &instance, &arg);
+  g_assert_true (ok);
+  g_assert_cmpfloat (arg.v_double, ==, G_PI);
+
+  arg.v_double = G_E;
+  ok = gi_field_info_set_field (field_info, &instance, &arg);
+  g_assert_true (ok);
+  g_assert_cmpfloat (instance.v_double, ==, G_E);
+
+  g_clear_pointer (&field_info, gi_base_info_unref);
+  g_clear_pointer (&union_info, gi_base_info_unref);
+}
+
+int
+main (int argc,
+      char *argv[])
+{
+  repository_init (&argc, &argv);
+
+  ADD_REPOSITORY_TEST ("/field-info/basic-struct-field", test_basic_struct_field, &typelib_load_spec_glib);
+  ADD_REPOSITORY_TEST ("/field-info/basic-union-field", test_basic_union_field, &typelib_load_spec_glib);
+  ADD_REPOSITORY_TEST ("/field-info/read-write-struct-field", test_read_write_struct_field, &typelib_load_spec_glib);
+  ADD_REPOSITORY_TEST ("/field-info/read-write-union-field", test_read_write_union_field, &typelib_load_spec_glib);
+
+  return g_test_run ();
+}
diff --git a/girepository/tests/meson.build b/girepository/tests/meson.build
index 2a75aac57..b804346fb 100644
--- a/girepository/tests/meson.build
+++ b/girepository/tests/meson.build
@@ -46,6 +46,9 @@ if enable_gir
     'callable-info' : {
       'depends': gio_gir_testing_dep,
     },
+    'field-info' : {
+      'depends': glib_gir_testing_dep,
+    },
     'function-info' : {
       'dependencies': [libffi_dep],
       'depends': glib_gir_testing_dep,