diff --git a/format.h b/format.h
index 8ce0116b..9e8c317f 100644
--- a/format.h
+++ b/format.h
@@ -2665,7 +2665,7 @@ inline void set_types(Value *, const Args & ...) {
 // argument that marks the end of the list.
 template <unsigned N>
 struct ArgArraySize {
-  enum { VALUE = N + (N == 0 || N > ArgList::MAX_PACKED_ARGS ? 1 : 0) };
+  enum { VALUE = N + (N == 0 || N >= ArgList::MAX_PACKED_ARGS ? 1 : 0) };
 };
 }
 }
diff --git a/test/format-test.cc b/test/format-test.cc
index d3bb023b..c75d31d2 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -574,6 +574,10 @@ TEST(FormatterTest, ManyArgs) {
                    FormatError, "argument index out of range");
   EXPECT_THROW_MSG(TestFormat<21>::format("{21}"),
                    FormatError, "argument index out of range");
+  enum { MAX_PACKED_ARGS = fmt::ArgList::MAX_PACKED_ARGS };
+  std::string format_str = fmt::format("{{{}}}", MAX_PACKED_ARGS + 1);
+  EXPECT_THROW_MSG(TestFormat<MAX_PACKED_ARGS>::format(format_str),
+                   FormatError, "argument index out of range");
 }
 #endif