diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 71c01f94997..8d7306a9749 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2018-08-01  Jonathan Wakely  <jwakely@redhat.com>
+
+	* configure: Regenerate.
+	* configure.ac: Add -D_GLIBCXX_ASSERTIONS to default DEBUG_FLAGS.
+	* src/c++11/futex.cc: Use __glibcxx_assert instead of
+	_GLIBCXX_DEBUG_ASSERT.
+
 2018-08-01  Mike Crowe  <mac@mcrowe.com>
 
 	* include/std/condition_variable (wait_for): Use steady_clock.
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 54a2e8a380e..d33081d544c 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -1571,7 +1571,7 @@ Optional Features:
   --enable-concept-checks use Boost-derived template checks [default=no]
   --enable-libstdcxx-debug-flags=FLAGS
                           pass compiler FLAGS when building debug library
-                          [default="-gdwarf-4 -g3 -O0"]
+                          [default="-gdwarf-4 -g3 -O0 -D_GLIBCXX_ASSERTIONS"]
   --enable-libstdcxx-debug
                           build extra debug library [default=no]
   --enable-cxx-flags=FLAGS
@@ -17932,7 +17932,7 @@ if test "${enable_libstdcxx_debug_flags+set}" = set; then :
       *)          as_fn_error "--enable-libstdcxx-debug-flags needs compiler flags as arguments" "$LINENO" 5 ;;
      esac
 else
-  enable_libstdcxx_debug_flags="-gdwarf-4 -g3 -O0"
+  enable_libstdcxx_debug_flags="-gdwarf-4 -g3 -O0 -D_GLIBCXX_ASSERTIONS"
 fi
 
 
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 1e0a33fb3ea..332af3706d3 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -168,7 +168,7 @@ GLIBCXX_ENABLE_LONG_LONG([yes])
 GLIBCXX_ENABLE_WCHAR_T([yes])
 GLIBCXX_ENABLE_C99([yes])
 GLIBCXX_ENABLE_CONCEPT_CHECKS([no])
-GLIBCXX_ENABLE_DEBUG_FLAGS(["-gdwarf-4 -g3 -O0"])
+GLIBCXX_ENABLE_DEBUG_FLAGS(["-gdwarf-4 -g3 -O0 -D_GLIBCXX_ASSERTIONS"])
 GLIBCXX_ENABLE_DEBUG([no])
 GLIBCXX_ENABLE_PARALLEL([yes])
 GLIBCXX_ENABLE_CXX_FLAGS
diff --git a/libstdc++-v3/src/c++11/futex.cc b/libstdc++-v3/src/c++11/futex.cc
index 278a5a80902..a5a8ec68c53 100644
--- a/libstdc++-v3/src/c++11/futex.cc
+++ b/libstdc++-v3/src/c++11/futex.cc
@@ -53,7 +53,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	// here on errors is abort.
 	int ret __attribute__((unused));
 	ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr);
-	_GLIBCXX_DEBUG_ASSERT(ret == 0 || errno == EINTR || errno == EAGAIN);
+	__glibcxx_assert(ret == 0 || errno == EINTR || errno == EAGAIN);
 	return true;
       }
     else
@@ -75,8 +75,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 	if (syscall (SYS_futex, __addr, futex_wait_op, __val, &rt) == -1)
 	  {
-	    _GLIBCXX_DEBUG_ASSERT(errno == EINTR || errno == EAGAIN
-				  || errno == ETIMEDOUT);
+	    __glibcxx_assert(errno == EINTR || errno == EAGAIN
+			     || errno == ETIMEDOUT);
 	    if (errno == ETIMEDOUT)
 	      return false;
 	  }