diff --git a/mozilla/nsprpub/pr/include/md/_solaris.h b/mozilla/nsprpub/pr/include/md/_solaris.h
index 616c666b6d1..21485a31663 100644
--- a/mozilla/nsprpub/pr/include/md/_solaris.h
+++ b/mozilla/nsprpub/pr/include/md/_solaris.h
@@ -48,8 +48,14 @@
 #undef _PR_HAVE_ATOMIC_OPS
 #else
 #define _PR_HAVE_ATOMIC_OPS
+/*
+ * We have assembly language implementation of atomic
+ * stacks for the sparc architecture only.
+ */
+#ifdef sparc
 #define _PR_HAVE_ATOMIC_CAS
 #endif
+#endif
 
 #define _PR_POLL_AVAILABLE
 #define _PR_USE_POLL