diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index ceaac2db195..4742ea41f8d 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,11 @@
+2018-11-11  Hans-Peter Nilsson  <hp@axis.com>
+
+	PR libstdc++-v3/54005
+	* include/bits/atomic_base.h (__atomic_base<_TTp>::is_lock_free(),
+	__atomic_base<_PTp*>::is_lock_free()): Call __atomic_always_lock_free
+	with the type-derived _S_alignment instead of __alignof the object.
+	* include/std/atomic (atomic<T>::is_lock_free()): Likewise.
+
 2018-11-11  Jonathan Wakely  <jwakely@redhat.com>
 
 	Implement P0318R1 unwrap_ref_decay and unwrap_reference
diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
index 7a3354d9e6f..57d51bf3fad 100644
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -355,7 +355,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	// Use a fake, minimally aligned pointer.
 	return __atomic_is_lock_free(sizeof(_M_i),
-	    reinterpret_cast<void *>(-__alignof(_M_i)));
+	    reinterpret_cast<void *>(-_S_alignment));
       }
 
       bool
@@ -363,7 +363,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	// Use a fake, minimally aligned pointer.
 	return __atomic_is_lock_free(sizeof(_M_i),
-	    reinterpret_cast<void *>(-__alignof(_M_i)));
+	    reinterpret_cast<void *>(-_S_alignment));
       }
 
       _GLIBCXX_ALWAYS_INLINE void
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 002604676cd..83206dc63a0 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -222,7 +222,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	// Produce a fake, minimally aligned pointer.
 	return __atomic_is_lock_free(sizeof(_M_i),
-	    reinterpret_cast<void *>(-__alignof(_M_i)));
+	    reinterpret_cast<void *>(-_S_alignment));
       }
 
       bool
@@ -230,7 +230,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	// Produce a fake, minimally aligned pointer.
 	return __atomic_is_lock_free(sizeof(_M_i),
-	    reinterpret_cast<void *>(-__alignof(_M_i)));
+	    reinterpret_cast<void *>(-_S_alignment));
       }
 
 #if __cplusplus >= 201703L