diff --git a/diff.c b/diff.c
index 85e714f6c6..e43519b885 100644
--- a/diff.c
+++ b/diff.c
@@ -346,9 +346,6 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	if (starts_with(var, "submodule."))
-		return parse_submodule_config_option(var, value);
-
 	if (git_diff_heuristic_config(var, value, cb) < 0)
 		return -1;
 
diff --git a/t/t4027-diff-submodule.sh b/t/t4027-diff-submodule.sh
index 518bf9524e..2ffd11a142 100755
--- a/t/t4027-diff-submodule.sh
+++ b/t/t4027-diff-submodule.sh
@@ -113,35 +113,6 @@ test_expect_success 'git diff HEAD with dirty submodule (work tree, refs match)'
 	! test -s actual4
 '
 
-test_expect_success 'git diff HEAD with dirty submodule (work tree, refs match) [.git/config]' '
-	git config diff.ignoreSubmodules all &&
-	git diff HEAD >actual &&
-	! test -s actual &&
-	git config submodule.subname.ignore none &&
-	git config submodule.subname.path sub &&
-	git diff HEAD >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subprev $subprev-dirty &&
-	test_cmp expect.body actual.body &&
-	git config submodule.subname.ignore all &&
-	git diff HEAD >actual2 &&
-	! test -s actual2 &&
-	git config submodule.subname.ignore untracked &&
-	git diff HEAD >actual3 &&
-	sed -e "1,/^@@/d" actual3 >actual3.body &&
-	expect_from_to >expect.body $subprev $subprev-dirty &&
-	test_cmp expect.body actual3.body &&
-	git config submodule.subname.ignore dirty &&
-	git diff HEAD >actual4 &&
-	! test -s actual4 &&
-	git diff HEAD --ignore-submodules=none >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subprev $subprev-dirty &&
-	test_cmp expect.body actual.body &&
-	git config --remove-section submodule.subname &&
-	git config --unset diff.ignoreSubmodules
-'
-
 test_expect_success 'git diff HEAD with dirty submodule (work tree, refs match) [.gitmodules]' '
 	git config diff.ignoreSubmodules dirty &&
 	git diff HEAD >actual &&
@@ -208,24 +179,6 @@ test_expect_success 'git diff HEAD with dirty submodule (untracked, refs match)'
 	! test -s actual4
 '
 
-test_expect_success 'git diff HEAD with dirty submodule (untracked, refs match) [.git/config]' '
-	git config submodule.subname.ignore all &&
-	git config submodule.subname.path sub &&
-	git diff HEAD >actual2 &&
-	! test -s actual2 &&
-	git config submodule.subname.ignore untracked &&
-	git diff HEAD >actual3 &&
-	! test -s actual3 &&
-	git config submodule.subname.ignore dirty &&
-	git diff HEAD >actual4 &&
-	! test -s actual4 &&
-	git diff --ignore-submodules=none HEAD >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subprev $subprev-dirty &&
-	test_cmp expect.body actual.body &&
-	git config --remove-section submodule.subname
-'
-
 test_expect_success 'git diff HEAD with dirty submodule (untracked, refs match) [.gitmodules]' '
 	git config --add -f .gitmodules submodule.subname.ignore all &&
 	git config --add -f .gitmodules submodule.subname.path sub &&
@@ -261,26 +214,6 @@ test_expect_success 'git diff between submodule commits' '
 	! test -s actual
 '
 
-test_expect_success 'git diff between submodule commits [.git/config]' '
-	git diff HEAD^..HEAD >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subtip $subprev &&
-	test_cmp expect.body actual.body &&
-	git config submodule.subname.ignore dirty &&
-	git config submodule.subname.path sub &&
-	git diff HEAD^..HEAD >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subtip $subprev &&
-	test_cmp expect.body actual.body &&
-	git config submodule.subname.ignore all &&
-	git diff HEAD^..HEAD >actual &&
-	! test -s actual &&
-	git diff --ignore-submodules=dirty HEAD^..HEAD >actual &&
-	sed -e "1,/^@@/d" actual >actual.body &&
-	expect_from_to >expect.body $subtip $subprev &&
-	git config --remove-section submodule.subname
-'
-
 test_expect_success 'git diff between submodule commits [.gitmodules]' '
 	git diff HEAD^..HEAD >actual &&
 	sed -e "1,/^@@/d" actual >actual.body &&