diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 3edc39ca2..c3938f2a0 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -42,7 +42,9 @@ path-constant BOOST_UNORDERED_TEST_DIR : . ;
 
 run quick.cpp ;
 
-compile debuggability/visualization_tests.cpp ;
+compile debuggability/visualization_tests.cpp
+  : <target-os>cygwin:<define>_X_OPEN_SOURCE=600
+  ;
 
 compile unordered/self_include_tests_obj.cpp
   : <define>BOOST_UNORDERED_HEADER="boost/unordered_map.hpp"
@@ -294,7 +296,7 @@ for local container in $(MMAP_CONTAINERS)
   : <define>BOOST_UNORDERED_FOA_MMAP_MAP_TYPE="boost::$(container)"
     <warnings>off
     <link>static
-    <target-os>cygwin:<build>no
+    <target-os>cygwin:<define>_X_OPEN_SOURCE=600
   : foa_mmap_$(container)_tests ;
 }
 
@@ -396,7 +398,7 @@ rule make_cfoa_interprocess_concurrency_tests ( name : defines ? )
           <toolset>clang-3.6:<build>no # idem
           <toolset>clang-3.7:<build>no # idem
           <toolset>clang-3.8:<build>no # idem
-          <target-os>cygwin:<build>no
+          <target-os>cygwin:<define>_X_OPEN_SOURCE=600
         : $(name) ;
 }