diff --git a/builtin/apply.c b/builtin/apply.c
index f6a3c97dd5..30eefc3c7b 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -2117,10 +2117,10 @@ static void update_pre_post_images(struct image *preimage,
 
 	/*
 	 * Adjust the common context lines in postimage. This can be
-	 * done in-place when we are just doing whitespace fixing,
-	 * which does not make the string grow, but needs a new buffer
-	 * when ignoring whitespace causes the update, since in this case
-	 * we could have e.g. tabs converted to multiple spaces.
+	 * done in-place when we are shrinking it with whitespace
+	 * fixing, but needs a new buffer when ignoring whitespace or
+	 * expanding leading tabs to spaces.
+	 *
 	 * We trust the caller to tell us if the update can be done
 	 * in place (postlen==0) or not.
 	 */
@@ -2185,7 +2185,7 @@ static int match_fragment(struct image *img,
 	int i;
 	char *fixed_buf, *buf, *orig, *target;
 	struct strbuf fixed;
-	size_t fixed_len;
+	size_t fixed_len, postlen;
 	int preimage_limit;
 
 	if (preimage->nr + try_lno <= img->nr) {
@@ -2335,6 +2335,7 @@ static int match_fragment(struct image *img,
 	strbuf_init(&fixed, preimage->len + 1);
 	orig = preimage->buf;
 	target = img->buf + try;
+	postlen = 0;
 	for (i = 0; i < preimage_limit; i++) {
 		size_t oldlen = preimage->line[i].len;
 		size_t tgtlen = img->line[try_lno + i].len;
@@ -2362,6 +2363,7 @@ static int match_fragment(struct image *img,
 		match = (tgtfix.len == fixed.len - fixstart &&
 			 !memcmp(tgtfix.buf, fixed.buf + fixstart,
 					     fixed.len - fixstart));
+		postlen += tgtfix.len;
 
 		strbuf_release(&tgtfix);
 		if (!match)
@@ -2399,8 +2401,10 @@ static int match_fragment(struct image *img,
 	 * hunk match.  Update the context lines in the postimage.
 	 */
 	fixed_buf = strbuf_detach(&fixed, &fixed_len);
+	if (postlen < postimage->len)
+		postlen = 0;
 	update_pre_post_images(preimage, postimage,
-			       fixed_buf, fixed_len, 0);
+			       fixed_buf, fixed_len, postlen);
 	return 1;
 
  unmatch_exit:
diff --git a/t/t4124-apply-ws-rule.sh b/t/t4124-apply-ws-rule.sh
index 581a801649..5d0c598338 100755
--- a/t/t4124-apply-ws-rule.sh
+++ b/t/t4124-apply-ws-rule.sh
@@ -486,4 +486,30 @@ test_expect_success 'same, but with CR-LF line endings && cr-at-eol unset' '
 	test_cmp one expect
 '
 
+test_expect_success 'whitespace=fix to expand' '
+	qz_to_tab_space >preimage <<-\EOF &&
+	QQa
+	QQb
+	QQc
+	ZZZZZZZZZZZZZZZZd
+	QQe
+	QQf
+	QQg
+	EOF
+	qz_to_tab_space >patch <<-\EOF &&
+	diff --git a/preimage b/preimage
+	--- a/preimage
+	+++ b/preimage
+	@@ -1,7 +1,6 @@
+	 QQa
+	 QQb
+	 QQc
+	-QQd
+	 QQe
+	 QQf
+	 QQg
+	EOF
+	git -c core.whitespace=tab-in-indent apply --whitespace=fix patch
+'
+
 test_done
diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index cdafd7e7c1..12f6b027ac 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh
@@ -17,7 +17,7 @@ test_expect_success 'setup: messages' '
 	vero eos et accusam et justo duo dolores et ea rebum.
 
 	EOF
-	q_to_tab <<-\EOF >>msg &&
+	qz_to_tab_space <<-\EOF >>msg &&
 	QDuis autem vel eum iriure dolor in hendrerit in vulputate velit
 	Qesse molestie consequat, vel illum dolore eu feugiat nulla facilisis
 	Qat vero eros et accumsan et iusto odio dignissim qui blandit
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index fa62d010f6..3fc9cc9288 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -91,6 +91,10 @@ q_to_tab () {
 	tr Q '\011'
 }
 
+qz_to_tab_space () {
+	tr QZ '\011\040'
+}
+
 append_cr () {
 	sed -e 's/$/Q/' | tr Q '\015'
 }