diff --git a/apis/python/src/tiledbsoma/pytiledbsoma.cc b/apis/python/src/tiledbsoma/pytiledbsoma.cc
index fa97811f04..0ac54a0a72 100644
--- a/apis/python/src/tiledbsoma/pytiledbsoma.cc
+++ b/apis/python/src/tiledbsoma/pytiledbsoma.cc
@@ -155,6 +155,11 @@ PYBIND11_MODULE(pytiledbsoma, m) {
                     *ctx->tiledb_ctx(),
                     attr_name,
                     ArrowAdapter::to_tiledb_format(attr_type));
+
+                if (ArrowAdapter::arrow_is_string_type(attr_type.c_str())) {
+                    attr.set_cell_val_num(TILEDB_VAR_NUM);
+                }
+
                 FilterList filter_list(*ctx->tiledb_ctx());
                 filter_list.add_filter(
                     Filter(*ctx->tiledb_ctx(), TILEDB_FILTER_ZSTD));
diff --git a/apis/python/tests/test_dataframe.py b/apis/python/tests/test_dataframe.py
index 8807ea2981..30b0861a63 100644
--- a/apis/python/tests/test_dataframe.py
+++ b/apis/python/tests/test_dataframe.py
@@ -1722,3 +1722,37 @@ def test_only_evolve_schema_when_enmr_is_extended(tmp_path):
     # subtract 1 for the __schema/__enumerations directory;
     # only looking at fragment files
     assert len(vfs.ls(os.path.join(uri, "__schema"))) - 1 == 3
+
+
+def test_fix_update_dataframe_with_var_strings(tmp_path):
+    uri = tmp_path.as_posix()
+
+    tbl = pa.table(
+        {
+            "soma_joinid": pa.array([0, 1, 2, 3], pa.int64()),
+            "mystring": pa.array(["a", "bb", "ccc", "dddd"], pa.large_utf8()),
+            "myint": pa.array([33, 44, 55, 66], pa.int32()),
+            "myfloat": pa.array([4.5, 5.5, 6.5, 7.5], pa.float32()),
+        }
+    )
+
+    with soma.DataFrame.create(uri, schema=tbl.schema) as sdf:
+        sdf.write(tbl)
+
+    with soma.DataFrame.open(uri, "r") as sdf:
+        updated_sdf = sdf.read().concat().to_pandas()
+    updated_sdf["newattr"] = np.array(["a", "b", "c", "d"])
+
+    with soma.DataFrame.open(uri, "w") as sdf:
+        soma.io.ingest._update_dataframe(
+            sdf,
+            updated_sdf,
+            "testing",
+            platform_config=None,
+            context=None,
+            default_index_name="mystring",
+        )
+
+    with soma.DataFrame.open(uri, "r") as sdf:
+        results = sdf.read().concat().to_pandas()
+        assert results.equals(updated_sdf)
diff --git a/libtiledbsoma/src/utils/arrow_adapter.cc b/libtiledbsoma/src/utils/arrow_adapter.cc
index ac2ea971e1..a89dff8fe2 100644
--- a/libtiledbsoma/src/utils/arrow_adapter.cc
+++ b/libtiledbsoma/src/utils/arrow_adapter.cc
@@ -822,7 +822,7 @@ ArraySchema ArrowAdapter::tiledb_schema_from_arrow_schema(
             auto schild = index_column_schema->children[i];
             auto col_name = schild->name;
             if (strcmp(child->name, col_name) == 0) {
-                if (ArrowAdapter::_isvar(child->format)) {
+                if (ArrowAdapter::arrow_is_string_type(child->format)) {
                     type = TILEDB_STRING_ASCII;
                 }
 
@@ -861,7 +861,7 @@ ArraySchema ArrowAdapter::tiledb_schema_from_arrow_schema(
                 attr.set_nullable(true);
             }
 
-            if (ArrowAdapter::_isvar(child->format)) {
+            if (ArrowAdapter::arrow_is_string_type(child->format)) {
                 attr.set_cell_val_num(TILEDB_VAR_NUM);
             }
 
@@ -872,7 +872,9 @@ ArraySchema ArrowAdapter::tiledb_schema_from_arrow_schema(
                     *ctx,
                     child->name,
                     enmr_type,
-                    ArrowAdapter::_isvar(enmr_format) ? TILEDB_VAR_NUM : 1,
+                    ArrowAdapter::arrow_is_string_type(enmr_format) ?
+                        TILEDB_VAR_NUM :
+                        1,
                     child->flags & ARROW_FLAG_DICTIONARY_ORDERED);
                 ArraySchemaExperimental::add_enumeration(*ctx, schema, enmr);
                 AttributeExperimental::set_enumeration_name(
@@ -919,7 +921,7 @@ ArraySchema ArrowAdapter::tiledb_schema_from_arrow_schema(
                     continue;
                 }
 
-                if (ArrowAdapter::_isvar(child->format)) {
+                if (ArrowAdapter::arrow_is_string_type(child->format)) {
                     // In the core API:
                     //
                     // * domain for strings must be set as (nullptr, nullptr)
@@ -1241,12 +1243,10 @@ ArrowAdapter::to_arrow(std::shared_ptr<ColumnBuffer> column) {
     return std::pair(std::move(array), std::move(schema));
 }
 
-bool ArrowAdapter::_isvar(const char* format) {
-    if ((strcmp(format, "U") == 0) || (strcmp(format, "Z") == 0) ||
-        (strcmp(format, "u") == 0) || (strcmp(format, "z") == 0)) {
-        return true;
-    }
-    return false;
+bool ArrowAdapter::arrow_is_string_type(const char* format) {
+    return (
+        (strcmp(format, "U") == 0) || (strcmp(format, "Z") == 0) ||
+        (strcmp(format, "u") == 0) || (strcmp(format, "z") == 0));
 }
 
 std::string_view ArrowAdapter::to_arrow_format(
diff --git a/libtiledbsoma/src/utils/arrow_adapter.h b/libtiledbsoma/src/utils/arrow_adapter.h
index 1cac805cc7..41af7c1c56 100644
--- a/libtiledbsoma/src/utils/arrow_adapter.h
+++ b/libtiledbsoma/src/utils/arrow_adapter.h
@@ -260,6 +260,15 @@ class ArrowAdapter {
     static std::string_view to_arrow_format(
         tiledb_datatype_t tiledb_dtype, bool use_large = true);
 
+    /**
+     * @brief Keystroke saver to determine whether Arrow type is of string,
+     * large string, binary, or large binary type.
+     *
+     * @param const char* Arrow data format
+     * @return bool Whether the Arrow type represents a string type
+     */
+    static bool arrow_is_string_type(const char* format);
+
     /**
      * @brief Get TileDB datatype from Arrow format string.
      *
@@ -673,8 +682,6 @@ class ArrowAdapter {
         return Dimension::create<T>(*ctx, name, {b[0], b[1]}, b[2]);
     }
 
-    static bool _isvar(const char* format);
-
     static FilterList _create_filter_list(
         std::string filters, std::shared_ptr<Context> ctx);