diff --git a/BaseTools/Source/C/Include/Common/BaseTypes.h b/BaseTools/Source/C/Include/Common/BaseTypes.h
index 31d0662085..150980b4c0 100644
--- a/BaseTools/Source/C/Include/Common/BaseTypes.h
+++ b/BaseTools/Source/C/Include/Common/BaseTypes.h
@@ -57,6 +57,16 @@
 #define NULL  ((VOID *) 0)
 #endif
 
+#ifdef __CC_ARM
+  //
+  // Older RVCT ARM compilers don't fully support #pragma pack and require __packed
+  // as a prefix for the structure.
+  //
+  #define PACKED  __packed
+#else
+  #define PACKED
+#endif
+
 //
 //  Support for variable length argument lists using the ANSI standard.
 //