diff --git a/t/t4124-apply-ws-rule.sh b/t/t4124-apply-ws-rule.sh
index 8d46df6c3a..aea052346e 100755
--- a/t/t4124-apply-ws-rule.sh
+++ b/t/t4124-apply-ws-rule.sh
@@ -121,6 +121,34 @@ test_expect_success 'whitespace=error-all, no rule (attribute)' '
 
 '
 
+test_expect_success 'spaces inserted by tab-in-indent' '
+
+	git config core.whitespace -trailing,-space,-indent,tab &&
+	rm -f .gitattributes &&
+	test_fix % &&
+	sed -e "s/_/ /g" -e "s/>/	/" <<-\EOF >expect &&
+		An_SP in an ordinary line>and a HT.
+		________A HT (%).
+		________A SP and a HT (@%).
+		_________A SP, a HT and a SP (@%).
+		_______Seven SP.
+		________Eight SP (#).
+		________Seven SP and a HT (@%).
+		________________Eight SP and a HT (@#%).
+		_________Seven SP, a HT and a SP (@%).
+		_________________Eight SP, a HT and a SP (@#%).
+		_______________Fifteen SP (#).
+		________________Fifteen SP and a HT (@#%).
+		________________Sixteen SP (#).
+		________________________Sixteen SP and a HT (@#%).
+		_____a__Five SP, a non WS, two SP.
+		A line with a (!) trailing SP_
+		A line with a (!) trailing HT>
+	EOF
+	test_cmp expect target
+
+'
+
 for t in - ''
 do
 	case "$t" in '') tt='!' ;; *) tt= ;; esac
diff --git a/ws.c b/ws.c
index d7b8c33f14..b282e8c100 100644
--- a/ws.c
+++ b/ws.c
@@ -362,12 +362,13 @@ void ws_fix_copy(struct strbuf *dst, const char *src, int len, unsigned ws_rule,
 		fixed = 1;
 	} else if ((ws_rule & WS_TAB_IN_INDENT) && last_tab_in_indent >= 0) {
 		/* Expand tabs into spaces */
+		int start = dst->len;
 		int last = last_tab_in_indent + 1;
 		for (i = 0; i < last; i++) {
 			if (src[i] == '\t')
 				do {
 					strbuf_addch(dst, ' ');
-				} while (dst->len % 8);
+				} while ((dst->len - start) % 8);
 			else
 				strbuf_addch(dst, src[i]);
 		}