diff --git a/src/core/ddsc/include/dds/dds.h b/src/core/ddsc/include/dds/dds.h
index db4a1d8740..b794c7c075 100644
--- a/src/core/ddsc/include/dds/dds.h
+++ b/src/core/ddsc/include/dds/dds.h
@@ -327,7 +327,7 @@ typedef struct dds_sample_info
   /** difference in generations between the sample and most recent sample of the same instance when read/take was called */
   uint32_t absolute_generation_rank;
   /** sequence number of the data (relative to the publisher); always 0 for invalid samples */
-  int64_t seq_no;
+  uint64_t seq_no;
 }
 dds_sample_info_t;
 
diff --git a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
index b3f3669bdf..da1c6f7646 100644
--- a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
@@ -42,7 +42,7 @@ struct ddsi_serdata {
   /* these get set by generic code after creating the serdata */
   ddsrt_wctime_t timestamp;
   uint32_t statusinfo;
-  int64_t seq_no;
+  seqno_t seq_no;
 
   /* FIXME: can I get rid of this one? */
   ddsrt_mtime_t twrite; /* write time, not source timestamp, set post-throttling */
diff --git a/src/core/ddsi/src/q_receive.c b/src/core/ddsi/src/q_receive.c
index 92c8e98dd4..ef84c0db91 100644
--- a/src/core/ddsi/src/q_receive.c
+++ b/src/core/ddsi/src/q_receive.c
@@ -1969,7 +1969,7 @@ static int handle_Gap (struct receiver_state *rst, ddsrt_etime_t tnow, struct nn
   return 1;
 }
 
-static struct ddsi_serdata *get_serdata (struct ddsi_sertype const * const type, const struct nn_rdata *fragchain, uint32_t sz, int justkey, unsigned statusinfo, ddsrt_wctime_t tstamp, int64_t seq_no)
+static struct ddsi_serdata *get_serdata (struct ddsi_sertype const * const type, const struct nn_rdata *fragchain, uint32_t sz, int justkey, unsigned statusinfo, ddsrt_wctime_t tstamp, seqno_t seq_no)
 {
   struct ddsi_serdata *sd = ddsi_serdata_from_ser (type, justkey ? SDK_KEY : SDK_DATA, fragchain, sz);
   if (sd)