diff --git a/src/htsback.c b/src/htsback.c
index c00bd8ef..646082a8 100644
--- a/src/htsback.c
+++ b/src/htsback.c
@@ -585,14 +585,6 @@ static int create_back_tmpfile(httrackp *opt, lien_back *const back,
   return 0;
 }
 
-/* Move src onto dst; RENAME does not clobber an existing target on Windows. */
-static hts_boolean replace_file(const char *src, const char *dst) {
-  if (RENAME(src, dst) == 0)
-    return HTS_TRUE;
-  (void) UNLINK(dst);
-  return RENAME(src, dst) == 0 ? HTS_TRUE : HTS_FALSE;
-}
-
 /* Commit or restore a re-fetch backup (#77 follow-up): a re-fetch over an
    existing file moved the good copy to back->tmpfile before truncating url_sav.
    commit keeps the new file and drops the backup; else restore it so an aborted
@@ -610,7 +602,7 @@ static void back_finalize_backup(httrackp *opt, lien_back *const back,
     }
     /* On failure keep the backup: an orphaned temp beats losing the good copy.
      */
-    if (!replace_file(back->tmpfile, back->url_sav))
+    if (!hts_rename_over(back->tmpfile, back->url_sav))
       hts_log_print(opt, LOG_WARNING | LOG_ERRNO,
                     "could not restore %s; previous copy kept as %s",
                     back->url_sav, back->tmpfile);
@@ -741,7 +733,7 @@ int back_finalize(httrackp * opt, cache_back * cache, struct_back * sback,
                                  "Read error when decompressing");
                     }
                     UNLINK(unpacked);
-                  } else if (replace_file(unpacked, back[p].url_sav)) {
+                  } else if (hts_rename_over(unpacked, back[p].url_sav)) {
                     /* The temp bypassed filecreate(), which is what chmods. */
 #ifndef _WIN32
                     chmod(back[p].url_sav, HTS_ACCESS_FILE);
diff --git a/src/htssinglefile.c b/src/htssinglefile.c
index 31a2f6ab..a65b9de2 100644
--- a/src/htssinglefile.c
+++ b/src/htssinglefile.c
@@ -1108,13 +1108,8 @@ hts_boolean singlefile_rewrite_file(httrackp *opt, const char *root,
       (void) chmod(fconv(catbuff, sizeof(catbuff), StringBuff(tmp)),
                    HTS_ACCESS_FILE);
 #endif
-    if (ok) {
-      /* RENAME does not clobber an existing target on Windows. */
-      if (RENAME(StringBuff(tmp), page_path) != 0) {
-        (void) UNLINK(page_path);
-        ok = RENAME(StringBuff(tmp), page_path) == 0 ? HTS_TRUE : HTS_FALSE;
-      }
-    }
+    if (ok)
+      ok = hts_rename_over(StringBuff(tmp), page_path);
     if (!ok) {
       hts_log_print(opt, LOG_ERROR, "single-file: could not rewrite %s",
                     page_path);
diff --git a/src/htstools.c b/src/htstools.c
index b4ea3859..8cb159e2 100644
--- a/src/htstools.c
+++ b/src/htstools.c
@@ -1443,3 +1443,15 @@ HTSEXT_API hts_boolean hts_findissystem(find_handle find) {
   }
   return 0;
 }
+
+hts_boolean hts_rename_over(const char *src, const char *dst) {
+  char csrc[CATBUFF_SIZE], cdst[CATBUFF_SIZE];
+
+  fconv(csrc, sizeof(csrc), src);
+  fconv(cdst, sizeof(cdst), dst);
+  if (RENAME(csrc, cdst) == 0)
+    return HTS_TRUE;
+  /* RENAME does not clobber an existing target on Windows. */
+  (void) UNLINK(cdst);
+  return RENAME(csrc, cdst) == 0 ? HTS_TRUE : HTS_FALSE;
+}
diff --git a/src/htstools.h b/src/htstools.h
index 7a6e1849..0548bfbc 100644
--- a/src/htstools.h
+++ b/src/htstools.h
@@ -137,6 +137,10 @@ HTSEXT_API hts_boolean hts_findisdir(find_handle find);
 HTSEXT_API hts_boolean hts_findisfile(find_handle find);
 HTSEXT_API hts_boolean hts_findissystem(find_handle find);
 
+/* Move src onto dst, replacing an existing dst; HTS_TRUE on success. Both
+   paths are fconv()'d. */
+hts_boolean hts_rename_over(const char *src, const char *dst);
+
 #endif
 
 #endif
diff --git a/src/htswarc.c b/src/htswarc.c
index 9f23b816..2b799dcc 100644
--- a/src/htswarc.c
+++ b/src/htswarc.c
@@ -964,16 +964,6 @@ static zipFile wacz_zip_open(const char *path) {
   return zipOpen2_64(path, 0 /*create*/, NULL, &ff);
 }
 
-/* Move src onto dst (UTF-8/Windows-safe); RENAME won't clobber on Windows, so
-   fall back to unlink+rename. Returns 0 on success. */
-static int wacz_rename_over(const char *src, const char *dst) {
-  char cs[CATBUFF_SIZE], cd[CATBUFF_SIZE];
-  if (RENAME(fconv(cs, sizeof(cs), src), fconv(cd, sizeof(cd), dst)) == 0)
-    return 0;
-  (void) UNLINK(fconv(cd, sizeof(cd), dst));
-  return RENAME(fconv(cs, sizeof(cs), src), fconv(cd, sizeof(cd), dst));
-}
-
 /* Package the segment(s) + .cdx + a generated pages.jsonl into <base>.wacz at
    crawl end (the archive file(s) and .cdx are already closed on disk). */
 static void warc_wacz_package(warc_writer *w) {
@@ -1092,7 +1082,7 @@ static void warc_wacz_package(warc_writer *w) {
     hts_log_print(w->opt, LOG_WARNING,
                   "WACZ: packaging failed, kept existing %s untouched",
                   waczpath);
-  } else if (wacz_rename_over(tmppath, waczpath) != 0) {
+  } else if (!hts_rename_over(tmppath, waczpath)) {
     (void) UNLINK(fconv(catbuff, sizeof(catbuff), tmppath));
     hts_log_print(w->opt, LOG_WARNING | LOG_ERRNO,
                   "WACZ: could not finalize %s", waczpath);
diff --git a/tests/43_local-update-truncate.test b/tests/43_local-update-truncate.test
index c3d6fe9a..4671688d 100644
--- a/tests/43_local-update-truncate.test
+++ b/tests/43_local-update-truncate.test
@@ -18,6 +18,7 @@ set -euo pipefail
 bash "$top_srcdir/tests/local-crawl.sh" \
     --rerun-args '--update -M400000' \
     --log-found 'More than 400000 bytes have been transferred.. giving up' \
+    --log-not-found 'could not restore' \
     --found bigtrunc/slow.bin \
     --file-min-bytes bigtrunc/slow.bin 655360 \
     --file-min-bytes bigtrunc/fast.bin 655360 \
diff --git a/tests/74_local-warc-wacz.test b/tests/74_local-warc-wacz.test
index 16c617a1..2e081799 100755
--- a/tests/74_local-warc-wacz.test
+++ b/tests/74_local-warc-wacz.test
@@ -5,11 +5,16 @@
 # real gate: STORE-mode entries, the fixed layout, recomputed sha256 digests and
 # the datapackage-digest chain (plus py-wacz/pywb when importable). The crawl
 # skips cleanly on a build without OpenSSL (no conformant SHA-256 -> no package).
+#
+# The cacheless second pass repackages over the .wacz the first one left: the
+# clobber, not the happy rename, is what breaks when a platform refuses to
+# rename onto an existing file (#726).
 
 set -eu
 
 : "${top_srcdir:=..}"
 
 bash "$top_srcdir/tests/local-crawl.sh" --errors 0 --wacz-validate \
+    --rerun-args '-C0' --log-not-found 'could not finalize' \
     --found 'mini304/index.html' --found 'mini304/page.html' \
     httrack 'BASEURL/mini304/index.html' --warc-file warc-out --wacz
diff --git a/tests/local-crawl.sh b/tests/local-crawl.sh
index ce3777a9..5ab3f41c 100755
--- a/tests/local-crawl.sh
+++ b/tests/local-crawl.sh
@@ -57,6 +57,8 @@ rerun_dead=
 tmpdir=
 serverpid=
 crawlpid=
+wacz_poisoned=
+wacz_poison="stale-wacz-that-a-second-pass-must-replace"
 
 function warning {
     echo "** $*" >&2
@@ -272,6 +274,14 @@ if test -n "$warc_validate"; then
     test -z "$w1" || cp "$w1" "${tmpdir}/warc-pass1.gz"
 fi
 
+# Poison the first-pass .wacz when a second pass follows: repackaging moves the
+# new archive over it, so the marker must be gone afterwards (#726). Poisoning
+# beats comparing the two packages, which can come out byte-identical.
+if test -n "$wacz_validate" && test -n "${rerun}${rerun_args}"; then
+    wacz_poisoned=$(find "$mirrorroot" -maxdepth 2 -name '*.wacz' 2>/dev/null | sort | tail -n1)
+    test -z "$wacz_poisoned" || echo "$wacz_poison" >"$wacz_poisoned"
+fi
+
 # --- optional second pass: re-mirror into the same dir (cache/update path) ----
 if test -n "$rerun"; then
     info "re-running httrack (update pass)"
@@ -416,6 +426,12 @@ if test -n "$wacz_validate"; then
         fi
         die "no .wacz file produced under $mirrorroot"
     fi
+    if test -n "$wacz_poisoned"; then
+        info "checking the second pass replaced the .wacz"
+        grep -q "$wacz_poison" "$wacz_poisoned" 2>/dev/null &&
+            die "stale .wacz kept: $wacz_poisoned"
+        result "OK"
+    fi
     validator=$(nativepath "${testdir}/wacz-validate.py")
     info "validating WACZ package"
     "$python" "$validator" "$(nativepath "$wacz")" >&2 || die "WACZ validation failed"