diff --git a/libc/stdio/fmt.c b/libc/stdio/fmt.c
index f5ea9739f22..0e44bbb46a0 100644
--- a/libc/stdio/fmt.c
+++ b/libc/stdio/fmt.c
@@ -272,8 +272,8 @@ static int __fmt_ntoa2(int out(const char *, void *, size_t), void *arg,
         digit &= (1u << log2base) - 1;
         value >>= log2base;
       }
-      if ((flags & FLAGS_GROUPING) && count == 3) {
-        buf[len++] = ',';
+      if ((flags & (FLAGS_GROUPING | FLAGS_QUOTE)) && count == 3) {
+        buf[len++] = (flags & FLAGS_QUOTE) ? '\'' : ',';
         count = 1;
       } else {
         count++;
@@ -289,7 +289,7 @@ static int __fmt_ntoa2(int out(const char *, void *, size_t), void *arg,
 static int __fmt_ntoa(int out(const char *, void *, size_t), void *arg,
                       uint128_t value, unsigned char signbit,
                       unsigned long log2base, unsigned long prec,
-                      unsigned long width, unsigned char flags,
+                      unsigned long width, unsigned flags,
                       const char *lang) {
   bool neg;
   uint128_t sign;
diff --git a/test/libc/stdio/snprintf_test.c b/test/libc/stdio/snprintf_test.c
index eeb520de556..cb82328242f 100644
--- a/test/libc/stdio/snprintf_test.c
+++ b/test/libc/stdio/snprintf_test.c
@@ -220,6 +220,6 @@ TEST(snprintf, testLongDoubleRounding) {
 TEST(snprintf, apostropheFlag) {
   char buf[20];
   int i = snprintf(buf, sizeof(buf), "%'d", 1000000);
-  ASSERT_EQ(7, i);
-  ASSERT_STREQ("1000000", buf);
+  ASSERT_EQ(9, i);
+  ASSERT_STREQ("1'000'000", buf);
 }