1 files changed, 4 insertions, 0 deletions
diff --git a/delta.c b/delta.c
index d5a5a8d..ccbccc5 100644
--- a/delta.c
+++ b/delta.c
@@ -445,6 +445,10 @@ static rs_result rs_delta_s_header(rs_job_t *job)
  */
 rs_job_t *rs_delta_begin(rs_signature_t *sig)
 {
+    /* Caller must have called rs_build_hash_table() by now */
+    if (!sig->tag_table)
+        rs_fatal("Must call rs_build_hash_table() prior to calling rs_delta_begin()");
+
     rs_job_t *job;
 
     job = rs_job_new("delta", rs_delta_s_header);