diff --git a/NEWS b/NEWS
index 3d588c546fdf1..ca31fe91d4dcf 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,8 @@ PHP                                                                        NEWS
 - IMAP:
   . Fixed bug #80239 (imap_rfc822_write_address() leaks memory). (cmb)
   . Fixed minor regression caused by fixing bug #80220. (cmb)
+  . Fixed bug #80242 (imap_mail_compose() segfaults for multipart with rfc822).
+    (cmb)
 
 - Opcache:
   . Fixed bug #80255 (Opcache bug (bad condition result) in 8.0.0rc1). (Nikita)
diff --git a/ext/imap/php_imap.c b/ext/imap/php_imap.c
index b13ce204fb278..258bd5bb9c9c3 100644
--- a/ext/imap/php_imap.c
+++ b/ext/imap/php_imap.c
@@ -3375,15 +3375,19 @@ PHP_FUNCTION(imap_mail_compose)
 					bod->disposition.parameter = disp_param;
 				}
 			}
-			if ((pvalue = zend_hash_str_find(Z_ARRVAL_P(data), "contents.data", sizeof("contents.data") - 1)) != NULL) {
-				convert_to_string_ex(pvalue);
-				bod->contents.text.data = fs_get(Z_STRLEN_P(pvalue) + 1);
-				memcpy(bod->contents.text.data, Z_STRVAL_P(pvalue), Z_STRLEN_P(pvalue) + 1);
-				bod->contents.text.size = Z_STRLEN_P(pvalue);
+			if (bod->type == TYPEMESSAGE && bod->subtype && !strcmp(bod->subtype, "RFC822")) {
+				bod->nested.msg = mail_newmsg();
 			} else {
-				bod->contents.text.data = fs_get(1);
-				memcpy(bod->contents.text.data, "", 1);
-				bod->contents.text.size = 0;
+				if ((pvalue = zend_hash_str_find(Z_ARRVAL_P(data), "contents.data", sizeof("contents.data") - 1)) != NULL) {
+					convert_to_string_ex(pvalue);
+					bod->contents.text.data = fs_get(Z_STRLEN_P(pvalue) + 1);
+					memcpy(bod->contents.text.data, Z_STRVAL_P(pvalue), Z_STRLEN_P(pvalue) + 1);
+					bod->contents.text.size = Z_STRLEN_P(pvalue);
+				} else {
+					bod->contents.text.data = fs_get(1);
+					memcpy(bod->contents.text.data, "", 1);
+					bod->contents.text.size = 0;
+				}
 			}
 			if ((pvalue = zend_hash_str_find(Z_ARRVAL_P(data), "lines", sizeof("lines") - 1)) != NULL) {
 				bod->size.lines = zval_get_long(pvalue);
@@ -3485,7 +3489,7 @@ PHP_FUNCTION(imap_mail_compose)
 
 				bod=&part->body;
 
-				spprintf(&tempstring, 0, "%s%s%s", mystring, bod->contents.text.data, CRLF);
+				spprintf(&tempstring, 0, "%s%s%s", mystring, bod->contents.text.data ? (char *) bod->contents.text.data : "", CRLF);
 				efree(mystring);
 				mystring=tempstring;
 			} while ((part = part->next)); /* until done */
diff --git a/ext/imap/tests/bug80242.phpt b/ext/imap/tests/bug80242.phpt
new file mode 100644
index 0000000000000..849e7c6212d03
--- /dev/null
+++ b/ext/imap/tests/bug80242.phpt
@@ -0,0 +1,22 @@
+--TEST--
+Bug #80242 (imap_mail_compose() segfaults for multipart with rfc822)
+--SKIPIF--
+<?php
+if (!extension_loaded('imap')) die('skip imap extension not available');
+?>
+--FILE--
+<?php
+$bodies = [[
+    'type' => TYPEMULTIPART,
+], [
+    'type' => TYPETEXT,
+    'contents.data' => 'some text',
+], [
+    'type' => TYPEMESSAGE,
+    'subtype' => 'RFC822',
+]];
+imap_mail_compose([], $bodies);
+echo "done\n";
+?>
+--EXPECT--
+done