diff --git a/matrepr/adapters/__init__.py b/matrepr/adapters/__init__.py
index c6b3a8b..82f870a 100644
--- a/matrepr/adapters/__init__.py
+++ b/matrepr/adapters/__init__.py
@@ -242,28 +242,28 @@ def get_row_labels(self) -> Optional[Iterable[Optional[int]]]:
             return None
 
         if self.dot_row is None:
-            return self.orig_row_labels if self.orig_row_labels else [str(i) for i in range(self.orig_shape[0])]
+            return self.orig_row_labels if self.orig_row_labels else list(range(self.orig_shape[0]))
         else:
             pre_dot_end, post_dot_start = self.get_dot_indices_row()
             if self.orig_row_labels is None:
                 # generate indices
                 # noinspection PyTypeChecker
-                return [str(i) for i in range(pre_dot_end)] + [None]\
-                    + [str(i) for i in range(post_dot_start, self.orig_shape[0])]
+                return list(range(pre_dot_end)) + [None]\
+                    + list(range(post_dot_start, self.orig_shape[0]))
             else:
                 return self.orig_row_labels[:pre_dot_end] + [None] \
                     + self.orig_row_labels[post_dot_start:self.orig_shape[0]]
 
     def get_col_labels(self) -> Iterable[Optional[int]]:
         if self.dot_col is None:
-            return self.orig_col_labels if self.orig_col_labels else [str(i) for i in range(self.orig_shape[1])]
+            return self.orig_col_labels if self.orig_col_labels else list(range(self.orig_shape[1]))
         else:
             pre_dot_end, post_dot_start = self.get_dot_indices_col()
             if self.orig_col_labels is None:
                 # generate indices
                 # noinspection PyTypeChecker
-                return [str(i) for i in range(pre_dot_end)] + [None]\
-                    + [str(i) for i in range(post_dot_start, self.orig_shape[1])]
+                return list(range(pre_dot_end)) + [None]\
+                    + list(range(post_dot_start, self.orig_shape[1]))
             else:
                 return self.orig_col_labels[:pre_dot_end] + [None] \
                     + self.orig_col_labels[post_dot_start:self.orig_shape[1]]
diff --git a/matrepr/html_formatter.py b/matrepr/html_formatter.py
index b717c73..66b3f9d 100644
--- a/matrepr/html_formatter.py
+++ b/matrepr/html_formatter.py
@@ -44,10 +44,13 @@ def _attributes_to_string(self, attributes: dict) -> str:
             ret = " " + ret
         return ret
 
-    def pprint(self, obj, current_indent=0):
+    def pprint(self, obj, current_indent=0, is_index=False):
         if obj is None:
             return ""
 
+        if is_index and isinstance(obj, int):
+            return int(obj)
+
         if isinstance(obj, (int, float)):
             return self.floatfmt(obj)
 
@@ -107,7 +110,7 @@ def _write_matrix(self, mat: MatrixAdapterRow,
                 self.write(f"<th></th>", indent=cell_indent)
             for col_label in mat.get_col_labels():
                 attr = ' style="text-align: center;"' if self.center_header else ""
-                self.write(f"<th{attr}>{self.pprint(col_label)}</th>", indent=cell_indent)
+                self.write(f"<th{attr}>{self.pprint(col_label, is_index=True)}</th>", indent=cell_indent)
             self.write("</tr>", indent=body_indent)
             self.write("</thead>", indent=body_indent)
 
@@ -116,7 +119,7 @@ def _write_matrix(self, mat: MatrixAdapterRow,
         for row_idx in range(nrows):
             self.write("<tr>", body_indent)
             if row_labels:
-                self.write(f"<th>{self.pprint(next(row_labels))}</th>", cell_indent)
+                self.write(f"<th>{self.pprint(next(row_labels), is_index=True)}</th>", cell_indent)
 
             col_range = (0, ncols)
             for col_idx, cell in enumerate(mat.get_dense_row(row_idx, col_range=col_range)):
diff --git a/matrepr/latex_formatter.py b/matrepr/latex_formatter.py
index 34efc6c..1a3ad12 100644
--- a/matrepr/latex_formatter.py
+++ b/matrepr/latex_formatter.py
@@ -64,10 +64,13 @@ def __init__(self, max_rows, max_cols, num_after_dots, title_latex, latex_matrix
             self.floatfmt = lambda f: python_scientific_to_latex_times10(format(f))
         self.indent_width = 4
 
-    def pprint(self, obj):
+    def pprint(self, obj, is_index=False):
         if obj is None:
             return ""
 
+        if is_index and isinstance(obj, int):
+            return int(obj)
+
         if isinstance(obj, (int, float)):
             return self.floatfmt(obj)
 
diff --git a/matrepr/list_converter.py b/matrepr/list_converter.py
index 8906e63..ae827e0 100644
--- a/matrepr/list_converter.py
+++ b/matrepr/list_converter.py
@@ -2,6 +2,8 @@
 # Use of this source code is governed by the BSD 2-clause license found in the LICENSE.txt file.
 # SPDX-License-Identifier: BSD-2-Clause
 
+from typing import List, Optional
+
 from .adapters import MatrixAdapter, MatrixAdapterRow, Truncated2DMatrix, to_trunc, DupeList
 from .base_formatter import unicode_dots
 
@@ -30,6 +32,12 @@ def _single_line(s: str) -> str:
     return " ".join(lines)
 
 
+def _to_str(iterable) -> Optional[List]:
+    if iterable is None:
+        return None
+    return [None if x is None else str(x) for x in iterable]
+
+
 class ListConverter:
     def __init__(self, max_rows, max_cols, num_after_dots, floatfmt, **_):
         super().__init__()
@@ -119,4 +127,6 @@ def to_lists_and_labels(self, mat: MatrixAdapter, is_1d_ok=True):
                 mat.get_shape()[1] > self.max_cols:
             mat = to_trunc(mat, self.max_rows, self.max_cols, self.num_after_dots)
 
-        return self._write_matrix(mat, is_vector=is_vector), mat.get_row_labels(), mat.get_col_labels()
+        return self._write_matrix(mat, is_vector=is_vector),\
+            _to_str(mat.get_row_labels()),\
+            _to_str(mat.get_col_labels())