diff --git a/tools/include/xen-tools/bitops.h b/tools/include/xen-tools/bitops.h
index 3b98fba6d7..29587e89fa 100644
--- a/tools/include/xen-tools/bitops.h
+++ b/tools/include/xen-tools/bitops.h
@@ -81,14 +81,15 @@ static inline int test_and_set_bit(unsigned long nr, void *addr)
     return oldbit;
 }
 
-static inline void bitmap_or(void *_dst, const void *_other,
+static inline void bitmap_or(void *_dst, const void *_src1, const void *_src2,
                              unsigned long nr_bits)
 {
     char *dst = _dst;
-    const char *other = _other;
+    const char *src1 = _src1, *src2 = _src2;
     unsigned long i;
+
     for ( i = 0; i < bitmap_size(nr_bits); ++i )
-        dst[i] |= other[i];
+        dst[i] = src1[i] | src2[i];
 }
 
 #endif  /* __XEN_TOOLS_BITOPS_H__ */
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 3b2c5222e4..fdbceab52e 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -668,7 +668,8 @@ static int suspend_and_send_dirty(struct xc_sr_context *ctx)
     else
         xc_set_progress_prefix(xch, "Checkpointed save");
 
-    bitmap_or(dirty_bitmap, ctx->save.deferred_pages, ctx->save.p2m_size);
+    bitmap_or(dirty_bitmap, dirty_bitmap, ctx->save.deferred_pages,
+              ctx->save.p2m_size);
 
     if ( !ctx->save.live && ctx->stream_type == XC_STREAM_COLO )
     {