diff --git a/test/strings/string.conversions/stof.pass.cpp b/test/strings/string.conversions/stof.pass.cpp
index 444a6951..65809cb2 100644
--- a/test/strings/string.conversions/stof.pass.cpp
+++ b/test/strings/string.conversions/stof.pass.cpp
@@ -6,6 +6,9 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: with_system_lib=x86_64-apple-darwin11
+// XFAIL: with_system_lib=x86_64-apple-darwin12
 
 // <string>
 
diff --git a/test/strings/string.conversions/stoll.pass.cpp b/test/strings/string.conversions/stoll.pass.cpp
index 3887b7d2..a4ba6a3b 100644
--- a/test/strings/string.conversions/stoll.pass.cpp
+++ b/test/strings/string.conversions/stoll.pass.cpp
@@ -6,6 +6,9 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: with_system_lib=x86_64-apple-darwin11
+// XFAIL: with_system_lib=x86_64-apple-darwin12
 
 // <string>