diff --git a/lib/expat_external.h b/lib/expat_external.h
--- a/lib/expat_external.h
+++ b/lib/expat_external.h
@@ -138,6 +138,7 @@
 #    endif
 #  endif

+#ifndef MOZILLA_CLIENT /* typedef XML_Char to char16_t */
 #  ifdef XML_UNICODE /* Information is UTF-16 encoded. */
 #    ifdef XML_UNICODE_WCHAR_T
 typedef wchar_t XML_Char;
@@ -150,6 +151,7 @@
 typedef char XML_Char;
 typedef char XML_LChar;
 #  endif   /* XML_UNICODE */
+#endif /* MOZILLA_CLIENT */

 #  ifdef XML_LARGE_SIZE /* Use large integers for file/stream positions. */
 typedef long long XML_Index;
diff --git a/lib/xmlparse.c b/lib/xmlparse.c
--- a/lib/xmlparse.c
+++ b/lib/xmlparse.c
@@ -195,6 +195,7 @@

 #endif

+#ifndef MOZILLA_CLIENT /* typedef XML_Char to char16_t */
 #ifdef XML_UNICODE

 #  ifdef XML_UNICODE_WCHAR_T
@@ -211,6 +212,7 @@
 #  define XML_L(x) x

 #endif
+#endif /* MOZILLA_CLIENT */

 /* Round up n to be a multiple of sz, where sz is a power of 2. */
 #define ROUND_UP(n, sz) (((n) + ((sz) - 1)) & ~((sz) - 1))