diff --git a/git/index/fun.py b/git/index/fun.py
index f40928c33..1012f4801 100644
--- a/git/index/fun.py
+++ b/git/index/fun.py
@@ -11,6 +11,7 @@
     S_ISDIR,
     S_IFMT,
     S_IFREG,
+    S_IXUSR,
 )
 import subprocess
 
@@ -115,7 +116,7 @@ def stat_mode_to_index_mode(mode):
         return S_IFLNK
     if S_ISDIR(mode) or S_IFMT(mode) == S_IFGITLINK:    # submodules
         return S_IFGITLINK
-    return S_IFREG | 0o644 | (mode & 0o111)       # blobs with or without executable bit
+    return S_IFREG | (mode & S_IXUSR and 0o755 or 0o644)  # blobs with or without executable bit
 
 
 def write_cache(entries: Sequence[Union[BaseIndexEntry, 'IndexEntry']], stream: IO[bytes],
diff --git a/test/test_fun.py b/test/test_fun.py
index a7fb8f8bc..e3d07194b 100644
--- a/test/test_fun.py
+++ b/test/test_fun.py
@@ -1,5 +1,5 @@
 from io import BytesIO
-from stat import S_IFDIR, S_IFREG, S_IFLNK
+from stat import S_IFDIR, S_IFREG, S_IFLNK, S_IXUSR
 from os import stat
 import os.path as osp
 from unittest import SkipTest
@@ -7,7 +7,8 @@
 from git import Git
 from git.index import IndexFile
 from git.index.fun import (
-    aggressive_tree_merge
+    aggressive_tree_merge,
+    stat_mode_to_index_mode,
 )
 from git.objects.fun import (
     traverse_tree_recursive,
@@ -206,6 +207,16 @@ def assert_entries(entries, num_entries, has_conflict=False):
             assert_entries(aggressive_tree_merge(odb, trees), 2, True)
         # END handle ours, theirs
 
+    def test_stat_mode_to_index_mode(self):
+        modes = (
+            0o600, 0o611, 0o640, 0o641, 0o644, 0o650, 0o651,
+            0o700, 0o711, 0o740, 0o744, 0o750, 0o751, 0o755,
+        )
+        for mode in modes:
+            expected_mode = S_IFREG | (mode & S_IXUSR and 0o755 or 0o644)
+            assert stat_mode_to_index_mode(mode) == expected_mode
+        # END for each mode
+
     def _assert_tree_entries(self, entries, num_trees):
         for entry in entries:
             assert len(entry) == num_trees