diff --git a/mozilla/xpcom/reflect/xptcall/src/md/unix/xptc_platforms_unixish_x86.h b/mozilla/xpcom/reflect/xptcall/src/md/unix/xptc_platforms_unixish_x86.h
index 1adc1579d9c..72002710fd0 100644
--- a/mozilla/xpcom/reflect/xptcall/src/md/unix/xptc_platforms_unixish_x86.h
+++ b/mozilla/xpcom/reflect/xptcall/src/md/unix/xptc_platforms_unixish_x86.h
@@ -131,7 +131,11 @@
 #define CFRONT_STYLE_THIS_ADJUST
 
 #elif defined(__sun__) || defined(__sun)
+#if defined(__GXX_ABI_VERSION) && __GXX_ABI_VERSION >= 100 /* G++ V3 ABI */
+#define THUNK_BASED_THIS_ADJUST
+#else
 #define CFRONT_STYLE_THIS_ADJUST
+#endif
 
 #elif defined(_WIN32)
 #define THUNK_BASED_THIS_ADJUST