diff --git a/ax_pthread.m4 b/ax_pthread.m4
index 9f35d1391..a9019832e 100644
--- a/ax_pthread.m4
+++ b/ax_pthread.m4
@@ -87,7 +87,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 31
+#serial 32
 
 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
 AC_DEFUN([AX_PTHREAD], [
@@ -249,7 +249,22 @@ AS_IF([test "x$ax_pthread_clang" = "xyes"],
 # correctly enabled
 
 case $host_os in
-        darwin* | hpux* | linux* | osf* | solaris*)
+        solaris*)
+        # Solaris 11.4 introduced XPG7 support and did away with the need for
+        # _REENTRANT.
+
+        AC_EGREP_CPP([AX_PTHREAD_SOLARIS__REENTRANT],
+            [
+#            undef _XOPEN_SOURCE
+#            include <sys/feature_tests.h>
+#            if _XOPEN_VERSION < 700
+             AX_PTHREAD_SOLARIS__REENTRANT
+#            endif
+            ],
+            [ax_pthread_check_macro="_REENTRANT"],
+            [ax_pthread_check_macro="--"])
+        ;;
+        darwin* | hpux* | linux* | osf*)
         ax_pthread_check_macro="_REENTRANT"
         ;;
 
diff --git a/configure b/configure
index 2f50d918a..7d9702d30 100755
--- a/configure
+++ b/configure
@@ -18415,7 +18415,31 @@ fi
 # correctly enabled
 
 case $host_os in
-        darwin* | hpux* | linux* | osf* | solaris*)
+        solaris*)
+        # Solaris 11.4 introduced XPG7 support and did away with the need for
+        # _REENTRANT.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            undef _XOPEN_SOURCE
+#            include <sys/feature_tests.h>
+#            if _XOPEN_VERSION < 700
+             AX_PTHREAD_SOLARIS__REENTRANT
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_SOLARIS__REENTRANT" >/dev/null 2>&1
+then :
+  ax_pthread_check_macro="_REENTRANT"
+else $as_nop
+  ax_pthread_check_macro="--"
+fi
+rm -rf conftest*
+
+        ;;
+        darwin* | hpux* | linux* | osf*)
         ax_pthread_check_macro="_REENTRANT"
         ;;