diff --git a/include/__config b/include/__config
index ef69bf495..a99fd16b9 100644
--- a/include/__config
+++ b/include/__config
@@ -1359,16 +1359,19 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #  define _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS  _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS
 #endif
 
-// Availability of stream API in the dylib got dropped and re-added.  The
-// extern template should effectively be available at:
-//    availability(macosx,introduced=10.9)
-//    availability(ios,introduced=7.0)
-#if defined(_LIBCPP_USE_AVAILABILITY_APPLE) &&                                 \
+// The stream API was dropped and re-added in the dylib shipped on macOS
+// and iOS. We can only assume the dylib to provide these definitions for
+// macosx >= 10.9 and ios >= 7.0. Otherwise, the definitions are available
+// from the headers, but not from the dylib. Explicit instantiation
+// declarations for streams exist conditionally to this; if we provide
+// an explicit instantiation declaration and we try to deploy to a dylib
+// that does not provide those symbols, we'll get a load-time error.
+#if !defined(_LIBCPP_BUILDING_LIBRARY) &&                                      \
     ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&                \
       __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1090) ||                 \
      (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&               \
       __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 70000))
-#define _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#  define _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 #endif
 
 #if defined(_LIBCPP_COMPILER_IBM)
diff --git a/include/istream b/include/istream
index 8487dbeba..efbbae800 100644
--- a/include/istream
+++ b/include/istream
@@ -1504,7 +1504,7 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
     return __is;
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<wchar_t>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_iostream<char>)
diff --git a/include/ostream b/include/ostream
index ef34f71c1..d7a5d5289 100644
--- a/include/ostream
+++ b/include/ostream
@@ -1092,7 +1092,7 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const bitset<_Size>& __x)
                          use_facet<ctype<_CharT> >(__os.getloc()).widen('1'));
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<wchar_t>)
 #endif
diff --git a/include/streambuf b/include/streambuf
index 1739d58a1..dd293dc63 100644
--- a/include/streambuf
+++ b/include/streambuf
@@ -486,7 +486,7 @@ basic_streambuf<_CharT, _Traits>::overflow(int_type)
     return traits_type::eof();
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<wchar_t>)
 
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get.pass.cpp
index c7f16ca7e..0f356e26d 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get.pass.cpp
@@ -7,8 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-
 // <istream>
 
 // int_type get();
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_chart.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_chart.pass.cpp
index b3d3c69b4..cf06e343b 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_chart.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_chart.pass.cpp
@@ -7,8 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-
 // <istream>
 
 // basic_istream<charT,traits>& get(char_type& c);
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size.pass.cpp
index a45802c57..bee448371 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size.pass.cpp
@@ -7,13 +7,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+// In macosx10.9 to macosx10.14, streams are provided in the dylib AND they
+// have a bug in how they handle null-termination in case of errors (see D40677).
 // XFAIL: with_system_cxx_lib=macosx10.13
 // XFAIL: with_system_cxx_lib=macosx10.12
 // XFAIL: with_system_cxx_lib=macosx10.11
 // XFAIL: with_system_cxx_lib=macosx10.10
 // XFAIL: with_system_cxx_lib=macosx10.9
-// XFAIL: with_system_cxx_lib=macosx10.8
-// XFAIL: with_system_cxx_lib=macosx10.7
 
 // <istream>
 
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size_chart.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size_chart.pass.cpp
index 437af84f9..c998680de 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size_chart.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/get_pointer_size_chart.pass.cpp
@@ -7,13 +7,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+// In macosx10.9 to macosx10.14, streams are provided in the dylib AND they
+// have a bug in how they handle null-termination in case of errors (see D40677).
 // XFAIL: with_system_cxx_lib=macosx10.13
 // XFAIL: with_system_cxx_lib=macosx10.12
 // XFAIL: with_system_cxx_lib=macosx10.11
 // XFAIL: with_system_cxx_lib=macosx10.10
 // XFAIL: with_system_cxx_lib=macosx10.9
-// XFAIL: with_system_cxx_lib=macosx10.8
-// XFAIL: with_system_cxx_lib=macosx10.7
 
 // <istream>
 
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size.pass.cpp
index 7ee2c2956..7ac350f9c 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size.pass.cpp
@@ -7,13 +7,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+// In macosx10.9 to macosx10.14, streams are provided in the dylib AND they
+// have a bug in how they handle null-termination in case of errors (see D40677).
 // XFAIL: with_system_cxx_lib=macosx10.13
 // XFAIL: with_system_cxx_lib=macosx10.12
 // XFAIL: with_system_cxx_lib=macosx10.11
 // XFAIL: with_system_cxx_lib=macosx10.10
 // XFAIL: with_system_cxx_lib=macosx10.9
-// XFAIL: with_system_cxx_lib=macosx10.8
-// XFAIL: with_system_cxx_lib=macosx10.7
 
 // <istream>
 
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size_chart.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size_chart.pass.cpp
index 1bce3fa5d..f4da497b2 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size_chart.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/getline_pointer_size_chart.pass.cpp
@@ -7,13 +7,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+// In macosx10.9 to macosx10.14, streams are provided in the dylib AND they
+// have a bug in how they handle null-termination in case of errors (see D40677).
 // XFAIL: with_system_cxx_lib=macosx10.13
 // XFAIL: with_system_cxx_lib=macosx10.12
 // XFAIL: with_system_cxx_lib=macosx10.11
 // XFAIL: with_system_cxx_lib=macosx10.10
 // XFAIL: with_system_cxx_lib=macosx10.9
-// XFAIL: with_system_cxx_lib=macosx10.8
-// XFAIL: with_system_cxx_lib=macosx10.7
 
 // <istream>
 
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/ignore_0xff.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/ignore_0xff.pass.cpp
index 3a37cffce..3095712b9 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/ignore_0xff.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/ignore_0xff.pass.cpp
@@ -7,9 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-// XFAIL: with_system_cxx_lib=macosx10.8
-
 // <istream>
 
 // basic_istream<charT,traits>&
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/read.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/read.pass.cpp
index ceef0d28f..20e70cfbd 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/read.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/read.pass.cpp
@@ -7,8 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-
 // <istream>
 
 // basic_istream<charT,traits>& read(char_type* s, streamsize n);
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/readsome.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/readsome.pass.cpp
index a0a8e2f1b..01eecb5d8 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/readsome.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/readsome.pass.cpp
@@ -7,9 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-// XFAIL: with_system_cxx_lib=macosx10.8
-
 // <istream>
 
 // streamsize readsome(char_type* s, streamsize n);
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg.pass.cpp
index e370b4bfb..dc4e0ba0d 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg.pass.cpp
@@ -7,9 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-// XFAIL: with_system_cxx_lib=macosx10.8
-
 // <istream>
 
 // basic_istream<charT,traits>& seekg(pos_type pos);
diff --git a/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg_off.pass.cpp b/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg_off.pass.cpp
index d41302e68..3b7417ab2 100644
--- a/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg_off.pass.cpp
+++ b/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg_off.pass.cpp
@@ -10,8 +10,6 @@
 // XFAIL: with_system_cxx_lib=macosx10.11
 // XFAIL: with_system_cxx_lib=macosx10.10
 // XFAIL: with_system_cxx_lib=macosx10.9
-// XFAIL: with_system_cxx_lib=macosx10.7
-// XFAIL: with_system_cxx_lib=macosx10.8
 
 // <istream>
 
diff --git a/test/std/numerics/complex.number/complex.ops/stream_input.pass.cpp b/test/std/numerics/complex.number/complex.ops/stream_input.pass.cpp
index 4d866acb8..24644e307 100644
--- a/test/std/numerics/complex.number/complex.ops/stream_input.pass.cpp
+++ b/test/std/numerics/complex.number/complex.ops/stream_input.pass.cpp
@@ -7,8 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: with_system_cxx_lib=macosx10.7
-
 // <complex>
 
 // template<class T, class charT, class traits>