diff --git a/ChangeLog b/ChangeLog
index 4e86c26883..464ab859c5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,7 +2,9 @@
                 ChangeLog file for zlib
 
 Changes in 1.3.2.1 (xx Feb 2026)
-- 
+- deflateBound() now includes the preset-dictionary Adler-32 when the stream
+  header has not yet been emitted, so the bound holds when a dictionary is
+  provided after deflateBound() and before the first deflate()
 
 Changes in 1.3.2 (17 Feb 2026)
 - Continued rewrite of CMake build [Vollstrecker]
diff --git a/deflate.c b/deflate.c
index a5be5e6947..c37a1e980a 100644
--- a/deflate.c
+++ b/deflate.c
@@ -885,7 +885,15 @@ z_size_t ZEXPORT deflateBound_z(z_streamp strm, z_size_t sourceLen) {
         wraplen = 0;
         break;
     case 1:                                 /* zlib wrapper */
-        wraplen = 6 + (s->strstart ? 4 : 0);
+        /* A preset dictionary adds four bytes of its Adler-32 right after
+           the two-byte header.  This can happen if a dictionary was already
+           provided (strstart is then non-zero), or if deflateBound() was
+           called before deflateSetDictionary() and the header has not yet
+           been emitted (status is still INIT_STATE, as no data has been
+           compressed).  Include the four bytes in the latter case as well,
+           so the returned bound covers the documented use of allocating an
+           output buffer for a single-pass deflate(). */
+        wraplen = 6 + (s->strstart || s->status == INIT_STATE ? 4 : 0);
         break;
 #ifdef GZIP
     case 2:                                 /* gzip wrapper */