diff --git a/src/config.h b/src/config.h
index 8041f7eb..1bc70a13 100644
--- a/src/config.h
+++ b/src/config.h
@@ -185,7 +185,7 @@ void setproctitle(const char *fmt, ...);
 #error "Undefined or invalid BYTE_ORDER"
 #endif
 
-#if (__i386 || __amd64) && __GNUC__
+#if (__i386 || __amd64 || __powerpc__) && __GNUC__
 #define GNUC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
 #if (GNUC_VERSION >= 40100) || defined(__clang__)
 #define HAVE_ATOMIC
diff --git a/src/zmalloc.c b/src/zmalloc.c
index d0cf726c..11616e5a 100644
--- a/src/zmalloc.c
+++ b/src/zmalloc.c
@@ -67,7 +67,10 @@ void zlibc_free(void *ptr) {
 #define free(ptr) je_free(ptr)
 #endif
 
-#ifdef HAVE_ATOMIC
+#if defined(__ATOMIC_RELAXED)
+#define update_zmalloc_stat_add(__n) __atomic_add_fetch(&used_memory, (__n), __ATOMIC_RELAXED)
+#define update_zmalloc_stat_sub(__n) __atomic_sub_fetch(&used_memory, (__n), __ATOMIC_RELAXED)
+#elif defined(HAVE_ATOMIC)
 #define update_zmalloc_stat_add(__n) __sync_add_and_fetch(&used_memory, (__n))
 #define update_zmalloc_stat_sub(__n) __sync_sub_and_fetch(&used_memory, (__n))
 #else
@@ -219,8 +222,8 @@ size_t zmalloc_used_memory(void) {
     size_t um;
 
     if (zmalloc_thread_safe) {
-#ifdef HAVE_ATOMIC
-        um = __sync_add_and_fetch(&used_memory, 0);
+#if defined(__ATOMIC_RELAXED) || defined(HAVE_ATOMIC)
+        um = update_zmalloc_stat_add(0);
 #else
         pthread_mutex_lock(&used_memory_mutex);
         um = used_memory;