diff --git a/compat/mingw.c b/compat/mingw.c
index e695aa102ed27e..bf552a2e364817 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -3486,6 +3486,22 @@ static PSID get_current_user_sid(void)
 	return result;
 }
 
+static int acls_supported(const char *path)
+{
+	size_t offset = offset_1st_component(path);
+	WCHAR wroot[MAX_PATH];
+	DWORD file_system_flags;
+
+	if (offset &&
+	    xutftowcs_path_ex(wroot, path, MAX_PATH, offset,
+			      MAX_PATH, 0) > 0 &&
+	    GetVolumeInformationW(wroot, NULL, 0, NULL, NULL,
+				  &file_system_flags, NULL, 0))
+		return !!(file_system_flags & FILE_PERSISTENT_ACLS);
+
+	return 0;
+}
+
 int is_path_owned_by_current_sid(const char *path)
 {
 	WCHAR wpath[MAX_PATH];
@@ -3541,7 +3557,14 @@ int is_path_owned_by_current_sid(const char *path)
 			 * okay, too.
 			 */
 			result = 1;
-		else if (git_env_bool("GIT_TEST_DEBUG_UNSAFE_DIRECTORIES", 0)) {
+		else if (IsWellKnownSid(sid, WinWorldSid) &&
+			 git_env_bool("GIT_TEST_DEBUG_UNSAFE_DIRECTORIES", 0) &&
+			 !acls_supported(path)) {
+			/*
+			 * On FAT32 volumes, ownership is not actually recorded.
+			 */
+			warning("'%s' is on a file system that does not record ownership", path);
+		} else if (git_env_bool("GIT_TEST_DEBUG_UNSAFE_DIRECTORIES", 0)) {
 			LPSTR str1, str2, to_free1 = NULL, to_free2 = NULL;
 
 			if (ConvertSidToStringSidA(sid, &str1))
diff --git a/setup.c b/setup.c
index a17282698c03f3..e9d04a42562720 100644
--- a/setup.c
+++ b/setup.c
@@ -1385,10 +1385,17 @@ const char *setup_git_directory_gently(int *nongit_ok)
 		if (!nongit_ok) {
 			struct strbuf prequoted = STRBUF_INIT;
 			struct strbuf quoted = STRBUF_INIT;
+			struct strbuf hint = STRBUF_INIT;
 
 #ifdef __MINGW32__
 			if (dir.buf[0] == '/')
 				strbuf_addstr(&prequoted, "%(prefix)/");
+			if (!git_env_bool("GIT_TEST_DEBUG_UNSAFE_DIRECTORIES", 0))
+				strbuf_addstr(&hint,
+					      _("\n\nSet the environment variable "
+						"GIT_TEST_DEBUG_UNSAFE_DIRECTORIES=true "
+						"and run\n"
+						"again for more information."));
 #endif
 
 			strbuf_add(&prequoted, dir.buf, dir.len);
@@ -1397,8 +1404,8 @@ const char *setup_git_directory_gently(int *nongit_ok)
 			die(_("unsafe repository ('%s' is owned by someone else)\n"
 			      "To add an exception for this directory, call:\n"
 			      "\n"
-			      "\tgit config --global --add safe.directory %s"),
-			    dir.buf, quoted.buf);
+			      "\tgit config --global --add safe.directory %s%s"),
+			    dir.buf, quoted.buf, hint.buf);
 		}
 		*nongit_ok = 1;
 		break;