diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3865,6 +3865,16 @@ int page_make_sharable(struct domain *d,
 
     spin_lock(&d->page_alloc_lock);
 
+    /* Check if the ref count is 2. The first from PGT_allocated, and the second
+     * from get_page at the top of this function */
+    if(page->count_info != (PGC_allocated | (2 + expected_refcnt)))
+    {
+        /* Return type count back to zero */
+        put_page(page);
+        spin_unlock(&d->page_alloc_lock);
+        return -E2BIG;
+    }
+
     /* Change page type and count atomically */
     y = page->u.inuse.type_info;
     nx = PGT_shared_page | PGT_validated | 1; 
@@ -3881,16 +3891,6 @@ int page_make_sharable(struct domain *d,
         y = cmpxchg(&page->u.inuse.type_info, x, nx);
     } while(x != y);
 
-    /* Check if the ref count is 2. The first from PGT_allocated, and the second
-     * from get_page at the top of this function */
-    if(page->count_info != (PGC_allocated | (2 + expected_refcnt)))
-    {
-        /* Return type count back to zero */
-        put_page_and_type(page);
-        spin_unlock(&d->page_alloc_lock);
-        return -E2BIG;
-    }
-
     page_set_owner(page, dom_cow);
     d->tot_pages--;
     page_list_del(page, &d->page_list);
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -545,7 +545,7 @@ int mem_sharing_nominate_page(struct dom
          * it a few lines above.
          * The mfn needs to revert back to rw type. This should never fail,
          * since no-one knew that the mfn was temporarily sharable */
-        ASSERT(page_make_private(d, page) == 0);
+        BUG_ON(page_make_private(d, page) != 0);
         mem_sharing_hash_destroy(hash_entry);
         mem_sharing_gfn_destroy(gfn_info, 0);
         shr_unlock();
@@ -699,7 +699,7 @@ gfn_found:
     unmap_domain_page(s);
     unmap_domain_page(t);
 
-    ASSERT(set_shared_p2m_entry(d, gfn, page_to_mfn(page)) != 0);
+    BUG_ON(set_shared_p2m_entry(d, gfn, page_to_mfn(page)) == 0);
     put_page_and_type(old_page);
 
 private_page_found: