Index: include/locale
===================================================================
--- include/locale
+++ include/locale
@@ -1402,6 +1402,7 @@
     this->__format_int(__fmt+1, __len, true, __iob.flags());
     const unsigned __nbuf = (numeric_limits<long>::digits / 3)
                           + ((numeric_limits<long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 2;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1428,6 +1429,7 @@
     this->__format_int(__fmt+1, __len, true, __iob.flags());
     const unsigned __nbuf = (numeric_limits<long long>::digits / 3)
                           + ((numeric_limits<long long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 2;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1454,6 +1456,7 @@
     this->__format_int(__fmt+1, __len, false, __iob.flags());
     const unsigned __nbuf = (numeric_limits<unsigned long>::digits / 3)
                           + ((numeric_limits<unsigned long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 1;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1480,6 +1483,7 @@
     this->__format_int(__fmt+1, __len, false, __iob.flags());
     const unsigned __nbuf = (numeric_limits<unsigned long long>::digits / 3)
                           + ((numeric_limits<unsigned long long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 1;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
Index: test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters.arithmetic/minmax_showbase.pass.cpp
===================================================================
--- /dev/null
+++ test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters.arithmetic/minmax_showbase.pass.cpp
@@ -0,0 +1,132 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <ostream>
+
+// template <class charT, class traits = char_traits<charT> >
+//   class basic_ostream;
+
+// operator<<(short n);
+// operator<<(unsigned short n);
+// operator<<(int n);
+// operator<<(unsigned int n);
+// operator<<(long n);
+// operator<<(unsigned long n);
+// operator<<(long long n);
+// operator<<(unsigned long long n);
+
+//  Testing to make sure that the max length values are correctly inserted when
+//  using std::showbase
+
+#include <cassert>
+#include <cstdint>
+#include <ios>
+#include <limits>
+#include <sstream>
+#include <type_traits>
+
+template <typename T>
+void test_min_oct(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::oct << std::showbase << std::numeric_limits<T>::min();
+    assert(ss.str() == expected);
+}
+
+template <typename T>
+void test_max_oct(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::oct << std::showbase << std::numeric_limits<T>::max();
+    assert(ss.str() == expected);
+}
+
+template <typename T>
+void test_min_dec(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::dec << std::showbase << std::numeric_limits<T>::min();
+    assert(ss.str() == expected);
+}
+
+template <typename T>
+void test_max_dec(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::dec << std::showbase << std::numeric_limits<T>::max();
+    assert(ss.str() == expected);
+}
+
+template <typename T>
+void test_min_hex(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::hex << std::showbase << std::numeric_limits<T>::min();
+    assert(ss.str() == expected);
+}
+
+template <typename T>
+void test_max_hex(const char *expected)
+{
+    std::stringstream ss;
+    ss << std::hex << std::showbase << std::numeric_limits<T>::max();
+    assert(ss.str() == expected);
+}
+
+int main(void)
+{
+    test_min_oct<short>("0100000");
+    test_min_dec<short>("-32768");
+    test_min_hex<short>("0x8000");
+
+    test_max_oct<unsigned short>("0177777");
+    test_max_dec<unsigned short>("65535");
+    test_max_hex<unsigned short>("0xffff");
+
+    test_min_oct<int>("020000000000");
+    test_min_dec<int>("-2147483648");
+    test_min_hex<int>("0x80000000");
+
+    test_max_oct<unsigned int>("037777777777");
+    test_max_dec<unsigned int>("4294967295");
+    test_max_hex<unsigned int>("0xffffffff");
+
+    const bool long_is_32 = std::integral_constant<bool, sizeof(long) == sizeof(int32_t)>::value; // avoid compiler warnings
+    const bool long_is_64 = std::integral_constant<bool, sizeof(long) == sizeof(int64_t)>::value; // avoid compiler warnings
+    const bool long_long_is_64 = std::integral_constant<bool, sizeof(long long) == sizeof(int64_t)>::value; // avoid compiler warnings
+
+    if (long_is_32) {
+        test_min_oct<long>("020000000000");
+        test_min_dec<long>("-2147483648");
+        test_min_hex<long>("0x80000000");
+
+        test_max_oct<unsigned long>("037777777777");
+        test_max_dec<unsigned long>("4294967295");
+        test_max_hex<unsigned long>("0xffffffff");
+    } else if (long_is_64) {
+        test_min_oct<long>("01000000000000000000000");
+        test_min_dec<long>("-9223372036854775808");
+        test_min_hex<long>("0x8000000000000000");
+
+        test_max_oct<unsigned long>("01777777777777777777777");
+        test_max_dec<unsigned long>("18446744073709551615");
+        test_max_hex<unsigned long>("0xffffffffffffffff");
+    }
+    if (long_long_is_64) {
+        test_min_oct<long long>("01000000000000000000000");
+        test_min_dec<long long>("-9223372036854775808");
+        test_min_hex<long long>("0x8000000000000000");
+
+        test_max_oct<unsigned long long>("01777777777777777777777");
+        test_max_dec<unsigned long long>("18446744073709551615");
+        test_max_hex<unsigned long long>("0xffffffffffffffff");
+    }
+
+    return 0;
+}