diff --git a/libc/include/regex.h b/libc/include/regex.h
index aec38e334..b06a515b4 100644
--- a/libc/include/regex.h
+++ b/libc/include/regex.h
@@ -42,8 +42,9 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
-/* types */
-typedef off_t regoff_t;
+/* POSIX says regoff_t is at least as large as the larger of ptrdiff_t and
+ * ssize_t. BSD uses off_t, but that interacts badly with _FILE_OFFSET_BITS. */
+typedef ssize_t regoff_t;
 
 typedef struct {
 	int re_magic;
diff --git a/tests/regex_test.cpp b/tests/regex_test.cpp
index d02622190..4a4409ef3 100644
--- a/tests/regex_test.cpp
+++ b/tests/regex_test.cpp
@@ -36,3 +36,13 @@ TEST(regex, smoke) {
 
   regfree(&re);
 }
+
+TEST(regex, match_offsets) {
+  regex_t re;
+  regmatch_t matches[1];
+  ASSERT_EQ(0, regcomp(&re, "b", 0));
+  ASSERT_EQ(0, regexec(&re, "abc", 1, matches, 0));
+  ASSERT_EQ(1, matches[0].rm_so);
+  ASSERT_EQ(2, matches[0].rm_eo);
+  regfree(&re);
+}