diff --git a/fmt/format.h b/fmt/format.h
index bcae5a21..9a6426e6 100644
--- a/fmt/format.h
+++ b/fmt/format.h
@@ -933,6 +933,7 @@ inline void format_decimal(Char *buffer, UInt value, unsigned num_digits,
   }
   unsigned index = static_cast<unsigned>(value * 2);
   *--buffer = Data::DIGITS[index + 1];
+  thousands_sep(buffer);
   *--buffer = Data::DIGITS[index];
 }
 
@@ -2780,7 +2781,7 @@ void BasicWriter<Char>::write_int(T value, Spec spec) {
     unsigned num_digits = internal::count_digits(abs_value);
     fmt::StringRef sep = internal::thousands_sep(std::localeconv());
     unsigned size = static_cast<unsigned>(
-          num_digits + sep.size() * (num_digits - 1) / 3);
+          num_digits + sep.size() * ((num_digits - 1) / 3));
     CharPtr p = prepare_int_buffer(size, spec, prefix, prefix_size) + 1;
     internal::format_decimal(get(p), abs_value, 0, internal::ThousandsSep(sep));
     break;
diff --git a/test/format-test.cc b/test/format-test.cc
index 4a0e85ce..89994c76 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1229,7 +1229,9 @@ TEST(FormatterTest, FormatIntLocale) {
   lconv lc = {};
   char sep[] = "--";
   lc.thousands_sep = sep;
-  EXPECT_CALL(mock, localeconv()).WillOnce(testing::Return(&lc));
+  EXPECT_CALL(mock, localeconv()).Times(3).WillRepeatedly(testing::Return(&lc));
+  EXPECT_EQ("123", format("{:n}", 123));
+  EXPECT_EQ("1--234", format("{:n}", 1234));
   EXPECT_EQ("1--234--567", format("{:n}", 1234567));
 }