diff --git a/src/indexer.c b/src/indexer.c
index 665d50fcd..e39345c71 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -325,6 +325,13 @@ on_error:
 	return -1;
 }
 
+GIT_INLINE(bool) has_entry(git_indexer *idx, git_oid *id)
+{
+	khiter_t k;
+	k = kh_get(oid, idx->pack->idx_cache, id);
+	return (k != kh_end(idx->pack->idx_cache));
+}
+
 static int save_entry(git_indexer *idx, struct entry *entry, struct git_pack_entry *pentry, git_off_t entry_start)
 {
 	int i, error;
@@ -339,8 +346,11 @@ static int save_entry(git_indexer *idx, struct entry *entry, struct git_pack_ent
 
 	pentry->offset = entry_start;
 	k = kh_put(oid, idx->pack->idx_cache, &pentry->sha1, &error);
-	if (!error)
+
+	if (error <= 0) {
+		giterr_set(GITERR_INDEXER, "cannot insert object into pack");
 		return -1;
+	}
 
 	kh_value(idx->pack->idx_cache, k) = pentry;
 
@@ -791,6 +801,9 @@ static int fix_thin_pack(git_indexer *idx, git_transfer_progress *stats)
 	git_oid_fromraw(&base, base_info);
 	git_mwindow_close(&w);
 
+	if (has_entry(idx, &base))
+		return 0;
+
 	if (inject_object(idx, &base) < 0)
 		return -1;
 
diff --git a/src/pack.c b/src/pack.c
index 5d0a27b91..105d67510 100644
--- a/src/pack.c
+++ b/src/pack.c
@@ -959,8 +959,15 @@ git_off_t get_delta_base(
 			if (k != kh_end(p->idx_cache)) {
 				*curpos += 20;
 				return ((struct git_pack_entry *)kh_value(p->idx_cache, k))->offset;
+			} else {
+				/* If we're building an index, don't try to find the pack
+				 * entry; we just haven't seen it yet.  We'll make
+				 * progress again in the next loop.
+				 */
+				return GIT_PASSTHROUGH;
 			}
 		}
+
 		/* The base entry _must_ be in the same pack */
 		if (pack_entry_find_offset(&base_offset, &unused, p, (git_oid *)base_info, GIT_OID_HEXSZ) < 0)
 			return packfile_error("base entry delta is not in the same pack");