diff --git a/plat/st/common/stm32mp_dt.c b/plat/st/common/stm32mp_dt.c
index 1cbf51b..282f53f 100644
--- a/plat/st/common/stm32mp_dt.c
+++ b/plat/st/common/stm32mp_dt.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2023, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2024, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -243,7 +243,11 @@
 		return 0U;
 	}
 
+#ifdef __aarch64__
+	size = (size_t)fdt_read_uint64_default(fdt, node, "st,mem-size", 0ULL);
+#else /* __aarch64__ */
 	size = (size_t)fdt_read_uint32_default(fdt, node, "st,mem-size", 0U);
+#endif /* __aarch64__ */
 
 	flush_dcache_range((uintptr_t)&size, sizeof(size_t));