diff --git a/src/include/port/atomics/generic-gcc.h b/src/include/port/atomics/generic-gcc.h
index ecabef3..da151a0 100644
--- a/src/include/port/atomics/generic-gcc.h
+++ b/src/include/port/atomics/generic-gcc.h
@@ -92,7 +92,8 @@
 /* generic gcc based atomic uint64 implementation */
 #if !defined(PG_HAVE_ATOMIC_U64_SUPPORT) \
 	&& !defined(PG_DISABLE_64_BIT_ATOMICS) \
-	&& (defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS))
+	&& (defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS)) \
+	&& (SIZEOF_VOID_P != 4)
 
 #define PG_HAVE_ATOMIC_U64_SUPPORT
 
@@ -194,7 +195,7 @@
 
 #if !defined(PG_DISABLE_64_BIT_ATOMICS)
 
-#if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
+#if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__ATOMIC_INT64_CAS) && (SIZEOF_VOID_P != 4)
 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
 static inline bool
 pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
@@ -205,7 +206,7 @@
 }
 #endif
 
-#if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
+#if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__SYNC_INT64_CAS) && (SIZEOF_VOID_P != 4)
 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
 static inline bool
 pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
@@ -220,7 +221,7 @@
 }
 #endif
 
-#if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
+#if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(HAVE_GCC__SYNC_INT64_CAS) && (SIZEOF_VOID_P != 4)
 #define PG_HAVE_ATOMIC_FETCH_ADD_U64
 static inline uint64
 pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)