diff --git a/dlls/ole32/storage32.h b/dlls/ole32/storage32.h
index 4fcfd9c..c628523 100644
--- a/dlls/ole32/storage32.h
+++ b/dlls/ole32/storage32.h
@@ -528,15 +528,23 @@
  */
 #ifdef WORDS_BIGENDIAN
 
+#ifndef htole32
 #define htole32(x) RtlUlongByteSwap(x)
+#endif
+#ifndef htole16
 #define htole16(x) RtlUshortByteSwap(x)
+#endif
 #define lendian32toh(x) RtlUlongByteSwap(x)
 #define lendian16toh(x) RtlUshortByteSwap(x)
 
 #else
 
+#ifndef htole32
 #define htole32(x) (x)
+#endif
+#ifndef htole16
 #define htole16(x) (x)
+#endif
 #define lendian32toh(x) (x)
 #define lendian16toh(x) (x)