diff --git a/clients/opal/models/send_receive/include/msg_format.h b/clients/opal/models/send_receive/include/msg_format.h
index e9676b28a..7de407a73 100644
--- a/clients/opal/models/send_receive/include/msg_format.h
+++ b/clients/opal/models/send_receive/include/msg_format.h
@@ -10,9 +10,11 @@
 
 #include <stdint.h>
 
-#ifndef BYTE_ORDER
+#ifdef __linux__
  #define _BSD_SOURCE    	1
  #include <endian.h>
+#elif !defined(BYTE_ORDER)
+ #error "Please define BYTE_ORDER"
 #endif
 
 #include "config.h"
@@ -70,6 +72,6 @@ struct msg
 		float f;	/**< Floating point values (note msg::endian) */
 		uint32_t i;	/**< Integer values (note msg::endian) */
 	} data[MSG_VALUES];
-} __attribute__((packed));
+} __attribute__((aligned(4), packed));
 
 #endif /* _MSG_FORMAT_H_ */
diff --git a/server/include/msg_format.h b/server/include/msg_format.h
index e9676b28a..7de407a73 100644
--- a/server/include/msg_format.h
+++ b/server/include/msg_format.h
@@ -10,9 +10,11 @@
 
 #include <stdint.h>
 
-#ifndef BYTE_ORDER
+#ifdef __linux__
  #define _BSD_SOURCE    	1
  #include <endian.h>
+#elif !defined(BYTE_ORDER)
+ #error "Please define BYTE_ORDER"
 #endif
 
 #include "config.h"
@@ -70,6 +72,6 @@ struct msg
 		float f;	/**< Floating point values (note msg::endian) */
 		uint32_t i;	/**< Integer values (note msg::endian) */
 	} data[MSG_VALUES];
-} __attribute__((packed));
+} __attribute__((aligned(4), packed));
 
 #endif /* _MSG_FORMAT_H_ */