diff --git a/runtime/src/kmp.h b/runtime/src/kmp.h
index 1fc3177..26dda9e 100644
--- a/runtime/src/kmp.h
+++ b/runtime/src/kmp.h
@@ -2507,7 +2507,7 @@
   union {
     kmp_uint8 flag; // flag as an unsigned char
     struct { // flag as a set of 8 bits
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
       /* Same fields as in the #else branch, but in reverse order */
       unsigned all : 1;
       unsigned unused : 3;
@@ -2672,7 +2672,7 @@
 #endif // BUILD_TIED_TASK_STACK
 
 typedef struct kmp_tasking_flags { /* Total struct must be exactly 32 bits */
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
   /* Same fields as in the #else branch, but in reverse order */
 #if OMPX_TASKGRAPH
   unsigned reserved31 : 6;
diff --git a/runtime/src/kmp_lock.h b/runtime/src/kmp_lock.h
index e2a0cda..6202f3d 100644
--- a/runtime/src/kmp_lock.h
+++ b/runtime/src/kmp_lock.h
@@ -120,7 +120,8 @@
 
 struct kmp_base_tas_lock {
   // KMP_LOCK_FREE(tas) => unlocked; locked: (gtid+1) of owning thread
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ && __LP64__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__) &&     \
+    __LP64__
   // Flip the ordering of the high and low 32-bit member to be consistent
   // with the memory layout of the address in 64-bit big-endian.
   kmp_int32 depth_locked; // depth locked, for nested locks only
diff --git a/runtime/test/tasking/bug_nested_proxy_task.c b/runtime/test/tasking/bug_nested_proxy_task.c
index 24fe1f3..9e0b412 100644
--- a/runtime/test/tasking/bug_nested_proxy_task.c
+++ b/runtime/test/tasking/bug_nested_proxy_task.c
@@ -50,7 +50,7 @@
      union {
         kmp_uint8 flag; // flag as an unsigned char
         struct { // flag as a set of 8 bits
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
           unsigned all : 1;
           unsigned unused : 3;
           unsigned set : 1;
diff --git a/runtime/test/tasking/bug_proxy_task_dep_waiting.c b/runtime/test/tasking/bug_proxy_task_dep_waiting.c
index 688860c..1e86d57 100644
--- a/runtime/test/tasking/bug_proxy_task_dep_waiting.c
+++ b/runtime/test/tasking/bug_proxy_task_dep_waiting.c
@@ -47,7 +47,7 @@
      union {
         kmp_uint8 flag; // flag as an unsigned char
         struct { // flag as a set of 8 bits
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
           unsigned all : 1;
           unsigned unused : 3;
           unsigned set : 1;
diff --git a/runtime/test/tasking/hidden_helper_task/common.h b/runtime/test/tasking/hidden_helper_task/common.h
index ba57656..68e2b58 100644
--- a/runtime/test/tasking/hidden_helper_task/common.h
+++ b/runtime/test/tasking/hidden_helper_task/common.h
@@ -17,7 +17,7 @@
   union {
     unsigned char flag;
     struct {
-#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
       unsigned all : 1;
       unsigned unused : 3;
       unsigned set : 1;