diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 8413d76582..e627140b85 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -79,12 +79,15 @@ static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws)
 		regmatch_t regmatch;
 		int flags = 0;
 
-		while (*data &&
+		while (sz && *data &&
 		       !regexec_buf(regexp, data, sz, 1, &regmatch, flags)) {
 			flags |= REG_NOTBOL;
 			data += regmatch.rm_eo;
-			if (*data && regmatch.rm_so == regmatch.rm_eo)
+			sz -= regmatch.rm_eo;
+			if (sz && *data && regmatch.rm_so == regmatch.rm_eo) {
 				data++;
+				sz--;
+			}
 			cnt++;
 		}
 
diff --git a/t/t4062-diff-pickaxe.sh b/t/t4062-diff-pickaxe.sh
index f0bf50bda7..7c4903f497 100755
--- a/t/t4062-diff-pickaxe.sh
+++ b/t/t4062-diff-pickaxe.sh
@@ -19,4 +19,9 @@ test_expect_success '-G matches' '
 	test 4096-zeroes.txt = "$(cat out)"
 '
 
+test_expect_success '-S --pickaxe-regex' '
+	git diff --name-only -S0 --pickaxe-regex HEAD^ >out &&
+	verbose test 4096-zeroes.txt = "$(cat out)"
+'
+
 test_done