diff --git a/src/libAtomVM/utils.h b/src/libAtomVM/utils.h
index 260adccfdf..6a102d1947 100644
--- a/src/libAtomVM/utils.h
+++ b/src/libAtomVM/utils.h
@@ -28,7 +28,7 @@
 #ifndef _UTILS_H_
 #define _UTILS_H_
 
-#ifdef __ORDER_LITTLE_ENDIAN__
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
     #ifdef __GNUC__
         #define READ_32_ALIGNED(ptr) \
             __builtin_bswap32(*((uint32_t *) (ptr)))
@@ -102,16 +102,40 @@
         #define ENDIAN_SWAP_32(value) ((((value) & 0xFF) << 24) | (((value) & 0xFF00) << 8) | (((value) & 0xFF0000) >> 8) | (((value) & 0xFF000000) >> 24))
     #endif
 
-#else
+#elif  __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    #define READ_64_UNALIGNED(ptr) \
+        ((uint64_t) ( (((uint8_t *)(ptr))[0] << 24) | (((uint8_t *) (ptr))[1] << 16) | (((uint8_t *)(ptr))[2] << 8) | ((uint8_t *)(ptr))[3] ) << 32 | \
+		(((uint8_t *)(ptr))[4] << 24) | (((uint8_t *) (ptr))[5] << 16) | (((uint8_t *)(ptr))[6] << 8) | ((uint8_t *)(ptr))[7] )
+
+    #ifdef __GNUC__
+        #define WRITE_64_UNALIGNED(ptr, val) \
+            { \
+                uint64_t val_arg = val; \
+                __builtin_memcpy(ptr, (void *) &val_arg, sizeof(uint64_t)); \
+            }
+
+        #define WRITE_32_UNALIGNED(ptr, val) \
+            { \
+                uint32_t val_arg = val; \
+                __builtin_memcpy(ptr, (void *) &val_arg, sizeof(uint32_t)); \
+            }
+    #else
+        #error Create implementations of WRITE_64_UNALIGNED
+        #define WRITE_32_UNALIGNED(ptr, val) \
+            { \
+                uint32_t val_arg = val; \
+                *((uint32_t *) (ptr)) = ( (((uint8_t *)(&val_arg))[0] << 24) | (((uint8_t *) (&val_arg))[1] << 16) | (((uint8_t *)(&val_arg))[2] << 8) | ((uint8_t *)(&val_arg))[3] ) \
+            }
+
+    #endif
+
+
     #define READ_32_ALIGNED(ptr) \
         (*((uint32_t *) (ptr)))
 
     #define READ_32_UNALIGNED(ptr) \
         ( (((uint8_t *)(ptr))[0] << 24) | (((uint8_t *) (ptr))[1] << 16) | (((uint8_t *)(ptr))[2] << 8) | ((uint8_t *)(ptr))[3] )
 
-    #define WRITE_32_UNALIGNED(ptr, val) \
-        *((uint32_t *) (ptr)) = ( (((uint8_t *)(&val))[0] << 24) | (((uint8_t *) (&val))[1] << 16) | (((uint8_t *)(&val))[2] << 8) | ((uint8_t *)(&val))[3] )
-
     #define READ_16_UNALIGNED(ptr) \
         ( (((uint8_t *)(ptr))[0] << 8) | ((uint8_t *)(ptr))[1] )
 
@@ -119,6 +143,9 @@
         *((uint16_t *) (ptr)) = ( (((uint8_t *)(&val))[0] << 8) | ((uint8_t *)(&val))[1] )
 
     #define ENDIAN_SWAP_32(value) (value)
+
+#else
+#error "unsupported endianness."
 #endif
 
 #define UNUSED(x) (void) (x);