Index: b/libev/ev.c
===================================================================
--- a/libev/ev.c
+++ b/libev/ev.c
@@ -617,9 +617,11 @@
   #if ECB_GCC_VERSION(4,7)
     /* see comment below (stdatomic.h) about the C11 memory model. */
     #define ECB_MEMORY_FENCE         __atomic_thread_fence (__ATOMIC_SEQ_CST)
-  #elif defined __clang && __has_feature (cxx_atomic)
+  #elif defined __clang
+   #if __has_feature (cxx_atomic)
     /* see comment below (stdatomic.h) about the C11 memory model. */
     #define ECB_MEMORY_FENCE         __c11_atomic_thread_fence (__ATOMIC_SEQ_CST)
+   #endif
   #elif ECB_GCC_VERSION(4,4) || defined __INTEL_COMPILER || defined __clang__
     #define ECB_MEMORY_FENCE         __sync_synchronize ()
   #elif _MSC_VER >= 1400 /* VC++ 2005 */