diff --git a/apply.c b/apply.c
index 2b7cd930efa..2bd59b63edd 100644
--- a/apply.c
+++ b/apply.c
@@ -101,7 +101,9 @@ int init_apply_state(struct apply_state *state,
 	state->ws_error_action = warn_on_ws_error;
 	state->ws_ignore_action = ignore_ws_none;
 	state->linenr = 1;
-	string_list_init_nodup(&state->fn_table);
+	string_list_init_nodup(&state->fs_fn_table);
+	state->fs_fn_table.cmp = fspathcmp;
+	string_list_init_nodup(&state->index_fn_table);
 	string_list_init_nodup(&state->limit_by_name);
 	strset_init(&state->removed_symlinks);
 	strset_init(&state->kept_symlinks);
@@ -122,7 +124,10 @@ void clear_apply_state(struct apply_state *state)
 	strset_clear(&state->kept_symlinks);
 	strbuf_release(&state->root);
 
-	/* &state->fn_table is cleared at the end of apply_patch() */
+	/*
+	 * &state->fs_fn_table and &state->index_fn_table are cleared at the
+	 * end of apply_patch()
+	 */
 }
 
 static void mute_routine(const char *msg, va_list params)
@@ -3270,14 +3275,28 @@ static int read_file_or_gitlink(const struct cache_entry *ce, struct strbuf *buf
 	return read_blob_object(buf, &ce->oid, ce->ce_mode);
 }
 
-static struct patch *in_fn_table(struct apply_state *state, const char *name)
+static struct patch *in_fs_fn_table(struct apply_state *state, const char *name)
 {
 	struct string_list_item *item;
 
 	if (!name)
 		return NULL;
 
-	item = string_list_lookup(&state->fn_table, name);
+	item = string_list_lookup(&state->fs_fn_table, name);
+	if (item)
+		return (struct patch *)item->util;
+
+	return NULL;
+}
+
+static struct patch *in_index_fn_table(struct apply_state *state, const char *name)
+{
+	struct string_list_item *item;
+
+	if (!name)
+		return NULL;
+
+	item = string_list_lookup(&state->index_fn_table, name);
 	if (item)
 		return (struct patch *)item->util;
 
@@ -3309,7 +3328,7 @@ static int was_deleted(struct patch *patch)
 	return patch == PATH_WAS_DELETED;
 }
 
-static void add_to_fn_table(struct apply_state *state, struct patch *patch)
+static void add_to_fn_tables(struct apply_state *state, struct patch *patch)
 {
 	struct string_list_item *item;
 
@@ -3319,7 +3338,9 @@ static void add_to_fn_table(struct apply_state *state, struct patch *patch)
 	 * file creations and copies
 	 */
 	if (patch->new_name) {
-		item = string_list_insert(&state->fn_table, patch->new_name);
+		item = string_list_insert(&state->fs_fn_table, patch->new_name);
+		item->util = patch;
+		item = string_list_insert(&state->index_fn_table, patch->new_name);
 		item->util = patch;
 	}
 
@@ -3328,7 +3349,9 @@ static void add_to_fn_table(struct apply_state *state, struct patch *patch)
 	 * later chunks shouldn't patch old names
 	 */
 	if ((patch->new_name == NULL) || (patch->is_rename)) {
-		item = string_list_insert(&state->fn_table, patch->old_name);
+		item = string_list_insert(&state->fs_fn_table, patch->old_name);
+		item->util = PATH_WAS_DELETED;
+		item = string_list_insert(&state->index_fn_table, patch->old_name);
 		item->util = PATH_WAS_DELETED;
 	}
 }
@@ -3341,7 +3364,9 @@ static void prepare_fn_table(struct apply_state *state, struct patch *patch)
 	while (patch) {
 		if ((patch->new_name == NULL) || (patch->is_rename)) {
 			struct string_list_item *item;
-			item = string_list_insert(&state->fn_table, patch->old_name);
+			item = string_list_insert(&state->fs_fn_table, patch->old_name);
+			item->util = PATH_TO_BE_DELETED;
+			item = string_list_insert(&state->index_fn_table, patch->old_name);
 			item->util = PATH_TO_BE_DELETED;
 		}
 		patch = patch->next;
@@ -3371,7 +3396,7 @@ static struct patch *previous_patch(struct apply_state *state,
 	if (patch->is_copy || patch->is_rename)
 		return NULL; /* "git" patches do not depend on the order */
 
-	previous = in_fn_table(state, patch->old_name);
+	previous = in_index_fn_table(state, patch->old_name);
 	if (!previous)
 		return NULL;
 
@@ -3681,7 +3706,7 @@ static int apply_data(struct apply_state *state, struct patch *patch,
 	}
 	patch->result = image.buf;
 	patch->resultsize = image.len;
-	add_to_fn_table(state, patch);
+	add_to_fn_tables(state, patch);
 	free(image.line_allocated);
 
 	if (0 < patch->is_delete && patch->resultsize)
@@ -3780,11 +3805,12 @@ static int check_preimage(struct apply_state *state,
 
 static int check_to_create(struct apply_state *state,
 			   const char *new_name,
-			   int ok_if_exists)
+			   int ok_if_exists_in_fs,
+			   int ok_if_exists_in_index)
 {
 	struct stat nst;
 
-	if (state->check_index && (!ok_if_exists || !state->cached)) {
+	if (state->check_index && (!ok_if_exists_in_index || !state->cached)) {
 		int pos;
 
 		pos = index_name_pos(state->repo->index, new_name, strlen(new_name));
@@ -3792,7 +3818,7 @@ static int check_to_create(struct apply_state *state,
 			struct cache_entry *ce = state->repo->index->cache[pos];
 
 			/* allow ITA, as they do not yet exist in the index */
-			if (!ok_if_exists && !(ce->ce_flags & CE_INTENT_TO_ADD))
+			if (!ok_if_exists_in_index && !(ce->ce_flags & CE_INTENT_TO_ADD))
 				return EXISTS_IN_INDEX;
 
 			/* ITA entries can never match working tree files */
@@ -3805,7 +3831,7 @@ static int check_to_create(struct apply_state *state,
 		return 0;
 
 	if (!lstat(new_name, &nst)) {
-		if (S_ISDIR(nst.st_mode) || ok_if_exists)
+		if (S_ISDIR(nst.st_mode) || ok_if_exists_in_fs)
 			return 0;
 		/*
 		 * A leading component of new_name might be a symlink
@@ -3915,7 +3941,8 @@ static int check_patch(struct apply_state *state, struct patch *patch)
 	const char *name = old_name ? old_name : new_name;
 	struct cache_entry *ce = NULL;
 	struct patch *tpatch;
-	int ok_if_exists;
+	int ok_if_exists_in_fs;
+	int ok_if_exists_in_index;
 	int status;
 
 	patch->rejected = 1; /* we will drop this after we succeed */
@@ -3938,16 +3965,29 @@ static int check_patch(struct apply_state *state, struct patch *patch)
 	 * B; ask to_be_deleted() about the later rename.  Removal of
 	 * B and rename from A to B is handled the same way by asking
 	 * was_deleted().
+	 *
+	 * These exemptions account for the core.ignorecase config -
+	 * a file that differs only by case is also considered "deleted"
+	 * if git is configured to ignore case. This means a case-only
+	 * rename, in a case-insensitive filesystem, is treated here as
+	 * a "self-swap" or mode change.
 	 */
-	if ((tpatch = in_fn_table(state, new_name)) &&
+	if ((tpatch = in_fs_fn_table(state, new_name)) &&
+	    (was_deleted(tpatch) || to_be_deleted(tpatch)))
+		ok_if_exists_in_fs = 1;
+	else
+		ok_if_exists_in_fs = 0;
+
+	if ((tpatch = in_index_fn_table(state, new_name)) &&
 	    (was_deleted(tpatch) || to_be_deleted(tpatch)))
-		ok_if_exists = 1;
+		ok_if_exists_in_index = 1;
 	else
-		ok_if_exists = 0;
+		ok_if_exists_in_index = 0;
 
 	if (new_name &&
 	    ((0 < patch->is_new) || patch->is_rename || patch->is_copy)) {
-		int err = check_to_create(state, new_name, ok_if_exists);
+		int err = check_to_create(state, new_name, ok_if_exists_in_fs,
+					  ok_if_exists_in_index);
 
 		if (err && state->threeway) {
 			patch->direct_to_threeway = 1;
@@ -4808,7 +4848,8 @@ static int apply_patch(struct apply_state *state,
 end:
 	free_patch_list(list);
 	strbuf_release(&buf);
-	string_list_clear(&state->fn_table, 0);
+	string_list_clear(&state->fs_fn_table, 0);
+	string_list_clear(&state->index_fn_table, 0);
 	return res;
 }
 
diff --git a/apply.h b/apply.h
index b9f18ce87d1..b520ce8c40a 100644
--- a/apply.h
+++ b/apply.h
@@ -95,8 +95,11 @@ struct apply_state {
 	/*
 	 * Records filenames that have been touched, in order to handle
 	 * the case where more than one patches touch the same file.
+	 * Two separate structures because with ignorecase, one of them
+	 * needs to be case-insensitive and the other not.
 	 */
-	struct string_list fn_table;
+	struct string_list fs_fn_table;
+	struct string_list index_fn_table;
 
 	/*
 	 * This is to save reporting routines before using
diff --git a/t/t4141-apply-icase.sh b/t/t4141-apply-icase.sh
index 17eb023a437..1c785133d16 100755
--- a/t/t4141-apply-icase.sh
+++ b/t/t4141-apply-icase.sh
@@ -30,7 +30,16 @@ test_expect_success setup '
        git diff HEAD HEAD^ -- file1 >deletion-patch &&
        git diff --cached HEAD -- file1 file2 >rename-file1-to-file2-patch &&
        git diff --cached HEAD -- file1 File1 >rename-file1-to-File1-patch &&
-       git diff --cached HEAD -- file0 >modify-file0-patch
+       git diff --cached HEAD -- file0 >modify-file0-patch &&
+
+       # then set up for swap
+       git reset --hard current &&
+       test_commit "swappable" file3 "different content for file3" swappable &&
+       file3blob=$(git rev-parse :file3) &&
+       git rm --cached file1 file3 &&
+       git update-index --add --cacheinfo 100644,$file1blob,File3 &&
+       git update-index --add --cacheinfo 100644,$file3blob,File1 &&
+       git diff --cached HEAD -- file1 file3 File1 File3 >swap-file1-and-file3-to-File3-and-File1-patch
 '
 
 # Basic creation, deletion, modification and renaming.
@@ -53,7 +62,7 @@ test_expect_success 'creation and deletion' '
        test_must_fail git rev-parse --verify :file1
 '
 
-test_expect_success 'modificaiton' '
+test_expect_success 'modification (index-only)' '
        # start at "initial" with file0 only
        git reset --hard initial &&
 
@@ -70,7 +79,7 @@ test_expect_success 'modificaiton' '
        test_cmp_rev :file0 "$file0blob"
 '
 
-test_expect_success 'rename file1 to file2' '
+test_expect_success 'rename file1 to file2 (index-only)' '
        # start from file0 and file1
        git reset --hard current &&
 
@@ -91,7 +100,7 @@ test_expect_success 'rename file1 to file2' '
        test_cmp_rev :file1 "$file1blob"
 '
 
-test_expect_success 'rename file1 to file2' '
+test_expect_success 'rename file1 to File1 (index-only)' '
        # start from file0 and file1
        git reset --hard current &&
 
@@ -112,17 +121,138 @@ test_expect_success 'rename file1 to file2' '
        test_cmp_rev :file1 "$file1blob"
 '
 
-# We may want to add tests with working tree here, without "--cached" and
-# with and without "--index" here.  For example, should modify-file0-patch
-# apply cleanly if we have File0 with $file0blob in the index and the working
-# tree if core.icase is set?
+# involve filesystem on renames
+test_expect_success 'rename file1 to File1 (with ignorecase, working tree)' '
+       # start from file0 and file1
+       git reset --hard current &&
+
+       # do the same with ignorecase
+       git -c core.ignorecase=true apply --index rename-file1-to-File1-patch &&
+       test_must_fail git rev-parse --verify :file1 &&
+       test_cmp_rev :File1 "$file1blob" &&
+       git -c core.ignorecase=true apply --index -R rename-file1-to-File1-patch &&
+       test_must_fail git rev-parse --verify :File1 &&
+       test_cmp_rev :file1 "$file1blob"
+'
+
+test_expect_success CASE_INSENSITIVE_FS 'rename file1 to File1 (without ignorecase, case-insensitive FS)' '
+       # start from file0 and file1
+       git reset --hard current &&
+
+       # rename file1 to File1 without ignorecase (fails as expected)
+       test_must_fail git -c core.ignorecase=false apply --index rename-file1-to-File1-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob"
+'
+
+test_expect_success !CASE_INSENSITIVE_FS 'rename file1 to File1 (without ignorecase, case-sensitive FS)' '
+       # start from file0 and file1
+       git reset --hard current &&
+
+       # rename file1 to File1 without ignorecase
+       git -c core.ignorecase=false apply --index rename-file1-to-File1-patch &&
+       test_must_fail git rev-parse --verify :file1 &&
+       test_cmp_rev :File1 "$file1blob" &&
+       git -c core.ignorecase=false apply --index -R rename-file1-to-File1-patch &&
+       test_must_fail git rev-parse --verify :File1 &&
+       test_cmp_rev :file1 "$file1blob"
+'
+
+test_expect_success 'rename file1 to file2 with working tree conflict' '
+       # start from file0 and file1, and file2 untracked
+       git reset --hard current &&
+       test_when_finished "rm file2" &&
+       touch file2 &&
+
+       # rename file1 to file2 with conflict
+       test_must_fail git -c core.ignorecase=false apply --index rename-file1-to-file2-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob" &&
 
-test_expect_success CASE_INSENSITIVE_FS 'a test only for icase fs' '
-       : sample
+       # do the same with ignorecase
+       test_must_fail git -c core.ignorecase=true apply --index rename-file1-to-file2-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob"
 '
 
-test_expect_success !CASE_INSENSITIVE_FS 'a test only for !icase fs' '
-       : sample
+test_expect_success 'rename file1 to file2 with case-insensitive conflict (index-only - ignorecase disabled)' '
+       # start from file0 and file1, and File2 in index
+       git reset --hard current &&
+       git update-index --add --cacheinfo 100644,$file3blob,File2 &&
+
+       # rename file1 to file2 without ignorecase
+       git -c core.ignorecase=false apply --cached rename-file1-to-file2-patch &&
+       test_must_fail git rev-parse --verify :file1 &&
+       test_cmp_rev :file2 "$file1blob" &&
+       git -c core.ignorecase=false apply --cached -R rename-file1-to-file2-patch &&
+       test_must_fail git rev-parse --verify :file2 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :File2 "$file3blob"
+'
+
+test_expect_failure 'rename file1 to file2 with case-insensitive conflict (index-only - ignorecase enabled)' '
+       # start from file0 and file1, and File2 in index
+       git reset --hard current &&
+       git update-index --add --cacheinfo 100644,$file3blob,File2 &&
+
+       # rename file1 to file2 with ignorecase, with a "File2" conflicting file in place - expect failure.
+       # instead of failure, we get success with "File1" and "file1" both existing in the index, despite
+       # the ignorecase configuration.
+       test_must_fail git -c core.ignorecase=true apply --cached rename-file1-to-file2-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :File2 "$file3blob"
+'
+
+test_expect_success 'rename file1 to File1 with case-sensitive conflict (index-only)' '
+       # start from file0 and file1, and File1 in index
+       git reset --hard current &&
+       git update-index --add --cacheinfo 100644,$file3blob,File1 &&
+
+       # On a case-insensitive filesystem with core.ignorecase on, a single git
+       # "reset --hard" will actually leave things wrong because of the
+       # index-to-working-tree discrepancy - see "reset --hard handles
+       # index-only case-insensitive duplicate" under t7104-reset-hard.sh.
+       # We are creating this unexpected state, so we should explicitly queue
+       # an extra reset. If reset ever starts to handle this case, this will
+       # become unnecessary but also not harmful.
+       test_when_finished "git reset --hard" &&
+
+       # rename file1 to File1 when File1 is already in index (fails with conflict)
+       test_must_fail git -c core.ignorecase=false apply --cached rename-file1-to-File1-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :File1 "$file3blob" &&
+
+       # do the same with ignorecase
+       test_must_fail git -c core.ignorecase=true apply --cached rename-file1-to-File1-patch &&
+       git rev-parse --verify :file1 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :File1 "$file3blob"
+'
+
+test_expect_success CASE_INSENSITIVE_FS 'case-insensitive swap - file1 to File2 and file2 to File1 (working tree)' '
+       # start from file0, file1, and file3
+       git reset --hard swappable &&
+
+       # "swap" file1 and file3 to case-insensitive versions without ignorecase on case-insensitive FS (fails as expected)
+       test_must_fail git -c core.ignorecase=false apply --index swap-file1-and-file3-to-File3-and-File1-patch &&
+       git rev-parse --verify :file1 &&
+       git rev-parse --verify :file3 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :file3 "$file3blob" &&
+
+       # do the same with ignorecase
+       git -c core.ignorecase=true apply --index swap-file1-and-file3-to-File3-and-File1-patch &&
+       test_must_fail git rev-parse --verify :file1 &&
+       test_must_fail git rev-parse --verify :file3 &&
+       test_cmp_rev :File3 "$file1blob" &&
+       test_cmp_rev :File1 "$file3blob" &&
+       git -c core.ignorecase=true apply --index -R swap-file1-and-file3-to-File3-and-File1-patch &&
+       test_must_fail git rev-parse --verify :File1 &&
+       test_must_fail git rev-parse --verify :File3 &&
+       test_cmp_rev :file1 "$file1blob" &&
+       test_cmp_rev :file3 "$file3blob"
 '
 
 test_done
