diff --git a/openchange-2.3-samba-4.15.patch b/openchange-2.3-samba-4.15.patch
new file mode 100644
index 0000000..13550d8
--- /dev/null
+++ b/openchange-2.3-samba-4.15.patch
@@ -0,0 +1,103 @@
+diff -up openchange-openchange-2.3-VULCAN/libmapi/IProfAdmin.c.samba-4.15 openchange-openchange-2.3-VULCAN/libmapi/IProfAdmin.c
+--- openchange-openchange-2.3-VULCAN/libmapi/IProfAdmin.c.samba-4.15	2021-07-19 12:26:37.615770488 +0200
++++ openchange-openchange-2.3-VULCAN/libmapi/IProfAdmin.c	2021-07-19 12:26:39.640771957 +0200
+@@ -794,7 +794,7 @@ _PUBLIC_ enum MAPISTATUS LoadProfile(str
+ 		cli_credentials_set_password(profile->credentials, profile->password, CRED_SPECIFIED);
+ 	}
+ 	if (use_krb != CRED_USE_KERBEROS_DESIRED) {
+-		cli_credentials_set_kerberos_state(profile->credentials, use_krb);
++		cli_credentials_set_kerberos_state(profile->credentials, use_krb, CRED_SPECIFIED);
+ 	}
+ 
+ 	return MAPI_E_SUCCESS;
+diff -up openchange-openchange-2.3-VULCAN/ndr_mapi.c.samba-4.15 openchange-openchange-2.3-VULCAN/ndr_mapi.c
+--- openchange-openchange-2.3-VULCAN/ndr_mapi.c.samba-4.15	2021-07-19 12:59:29.801210983 +0200
++++ openchange-openchange-2.3-VULCAN/ndr_mapi.c	2021-07-19 13:07:49.382594567 +0200
+@@ -1235,15 +1235,18 @@ _PUBLIC_ enum ndr_err_code ndr_pull_EcDo
+ 	TALLOC_CTX	*_mem_save_rgbAuxOut_1;
+ 
+ 	if (flags & NDR_IN) {
++		uint32_t array_length = 0, array_size = 0;
+ 		OC_ZERO_STRUCT(r->out);
+ 
+ 		NDR_CHECK(ndr_pull_array_size(ndr, &r->in.szUserDN));
+ 		NDR_CHECK(ndr_pull_array_length(ndr, &r->in.szUserDN));
+-		if (ndr_get_array_length(ndr, &r->in.szUserDN) > ndr_get_array_size(ndr, &r->in.szUserDN)) {
+-			return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", ndr_get_array_size(ndr, &r->in.szUserDN), ndr_get_array_length(ndr, &r->in.szUserDN));
++		NDR_CHECK(ndr_get_array_length(ndr, &r->in.szUserDN, &array_length));
++		NDR_CHECK(ndr_get_array_size(ndr, &r->in.szUserDN, &array_size));
++		if (array_length > array_size) {
++			return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", array_size, array_length);
+ 		}
+-		NDR_CHECK(ndr_check_string_terminator(ndr, ndr_get_array_length(ndr, &r->in.szUserDN), sizeof(uint8_t)));
+-		NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, &r->in.szUserDN, ndr_get_array_length(ndr, &r->in.szUserDN), sizeof(uint8_t), CH_DOS));
++		NDR_CHECK(ndr_check_string_terminator(ndr, array_length, sizeof(uint8_t)));
++		NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, &r->in.szUserDN, array_length, sizeof(uint8_t), CH_DOS));
+ 		NDR_CHECK(ndr_pull_uint32(ndr, NDR_SCALARS, &r->in.ulFlags));
+ 		NDR_CHECK(ndr_pull_uint32(ndr, NDR_SCALARS, &r->in.ulConMod));
+ 		NDR_CHECK(ndr_pull_uint32(ndr, NDR_SCALARS, &r->in.cbLimit));
+@@ -1317,6 +1320,7 @@ _PUBLIC_ enum ndr_err_code ndr_pull_EcDo
+ 	}
+ 
+ 	if (flags & NDR_OUT) {
++		uint32_t array_length = 0, array_size = 0;
+ 		if (ndr->flags & LIBNDR_FLAG_REF_ALLOC) {
+ 			NDR_PULL_ALLOC(ndr, r->out.handle);
+ 		}
+@@ -1366,11 +1370,13 @@ _PUBLIC_ enum ndr_err_code ndr_pull_EcDo
+ 			NDR_PULL_SET_MEM_CTX(ndr, *r->out.szDNPrefix, 0);
+ 			NDR_CHECK(ndr_pull_array_size(ndr, r->out.szDNPrefix));
+ 			NDR_CHECK(ndr_pull_array_length(ndr, r->out.szDNPrefix));
+-			if (ndr_get_array_length(ndr, r->out.szDNPrefix) > ndr_get_array_size(ndr, r->out.szDNPrefix)) {
+-				return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", ndr_get_array_size(ndr, r->out.szDNPrefix), ndr_get_array_length(ndr, r->out.szDNPrefix));
++			NDR_CHECK(ndr_get_array_length(ndr, r->out.szDNPrefix, &array_length));
++			NDR_CHECK(ndr_get_array_size(ndr, r->out.szDNPrefix, &array_size));
++			if (array_length > array_size) {
++				return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", array_size, array_length);
+ 			}
+-			NDR_CHECK(ndr_check_string_terminator(ndr, ndr_get_array_length(ndr, r->out.szDNPrefix), sizeof(uint8_t)));
+-			NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, r->out.szDNPrefix, ndr_get_array_length(ndr, r->out.szDNPrefix), sizeof(uint8_t), CH_DOS));
++			NDR_CHECK(ndr_check_string_terminator(ndr, array_length, sizeof(uint8_t)));
++			NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, r->out.szDNPrefix, array_length, sizeof(uint8_t), CH_DOS));
+ 			NDR_PULL_SET_MEM_CTX(ndr, _mem_save_szDNPrefix_1, 0);
+ 		}
+ 		NDR_PULL_SET_MEM_CTX(ndr, _mem_save_szDNPrefix_0, LIBNDR_FLAG_REF_ALLOC);
+@@ -1391,11 +1397,13 @@ _PUBLIC_ enum ndr_err_code ndr_pull_EcDo
+ 			NDR_PULL_SET_MEM_CTX(ndr, *r->out.szDisplayName, 0);
+ 			NDR_CHECK(ndr_pull_array_size(ndr, r->out.szDisplayName));
+ 			NDR_CHECK(ndr_pull_array_length(ndr, r->out.szDisplayName));
+-			if (ndr_get_array_length(ndr, r->out.szDisplayName) > ndr_get_array_size(ndr, r->out.szDisplayName)) {
+-				return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", ndr_get_array_size(ndr, r->out.szDisplayName), ndr_get_array_length(ndr, r->out.szDisplayName));
++			NDR_CHECK(ndr_get_array_length(ndr, r->out.szDisplayName, &array_length));
++			NDR_CHECK(ndr_get_array_size(ndr, r->out.szDisplayName, &array_size));
++			if (array_length > array_size) {
++				return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", array_size, array_length);
+ 			}
+-			NDR_CHECK(ndr_check_string_terminator(ndr, ndr_get_array_length(ndr, r->out.szDisplayName), sizeof(uint8_t)));
+-			NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, r->out.szDisplayName, ndr_get_array_length(ndr, r->out.szDisplayName), sizeof(uint8_t), CH_DOS));
++			NDR_CHECK(ndr_check_string_terminator(ndr, array_length, sizeof(uint8_t)));
++			NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, r->out.szDisplayName, array_length, sizeof(uint8_t), CH_DOS));
+ 			NDR_PULL_SET_MEM_CTX(ndr, _mem_save_szDisplayName_1, 0);
+ 		}
+ 		NDR_PULL_SET_MEM_CTX(ndr, _mem_save_szDisplayName_0, LIBNDR_FLAG_REF_ALLOC);
+@@ -1415,14 +1423,16 @@ _PUBLIC_ enum ndr_err_code ndr_pull_EcDo
+ 		NDR_PULL_SET_MEM_CTX(ndr, _mem_save_pulTimeStamp_0, LIBNDR_FLAG_REF_ALLOC);
+ 		NDR_CHECK(ndr_pull_array_size(ndr, &r->out.rgbAuxOut));
+ 		NDR_CHECK(ndr_pull_array_length(ndr, &r->out.rgbAuxOut));
+-		if (ndr_get_array_length(ndr, &r->out.rgbAuxOut) > ndr_get_array_size(ndr, &r->out.rgbAuxOut)) {
+-			return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", ndr_get_array_size(ndr, &r->out.rgbAuxOut), ndr_get_array_length(ndr, &r->out.rgbAuxOut));
++		NDR_CHECK(ndr_get_array_length(ndr, &r->out.rgbAuxOut, &array_length));
++		NDR_CHECK(ndr_get_array_size(ndr, &r->out.rgbAuxOut, &array_size));
++		if (array_length > array_size) {
++			return ndr_pull_error(ndr, NDR_ERR_ARRAY_SIZE, "Bad array size %u should exceed array length %u", array_size, array_length);
+ 		}
+ 		if (ndr->flags & LIBNDR_FLAG_REF_ALLOC) {
+-			NDR_PULL_ALLOC_N(ndr, r->out.rgbAuxOut, ndr_get_array_size(ndr, &r->out.rgbAuxOut));
++			NDR_PULL_ALLOC_N(ndr, r->out.rgbAuxOut, array_size);
+ 		}
+ 		/* Only try to pull rgbAuxOut if the fake array size is > 0 */
+-		if (ndr_get_array_size(ndr, &r->out.rgbAuxOut)) {
++		if (array_size) {
+ 			_mem_save_rgbAuxOut_1 = NDR_PULL_GET_MEM_CTX(ndr);
+ 			NDR_PULL_SET_MEM_CTX(ndr, r->out.rgbAuxOut, 0);
+ 			NDR_CHECK(ndr_pull_mapi2k7_AuxInfo(ndr, NDR_SCALARS, r->out.rgbAuxOut));
diff --git a/openchange.spec b/openchange.spec
index 60e6dc9..ba9c139 100644
--- a/openchange.spec
+++ b/openchange.spec
@@ -23,7 +23,7 @@
 
 Name: openchange
 Version: 2.3
-Release: 37%{?dist}
+Release: 38%{?dist}
 Summary: Provides access to Microsoft Exchange servers using native protocols
 License: GPLv3+ and Public Domain
 URL: http://www.openchange.org/
@@ -101,6 +101,7 @@ Patch19: openchange-2.3-autoconf-2.71.patch
 %if !%{build_server_package}
 Patch20: openchange-2.3-disable-server-reqs.patch
 %endif
+Patch21: openchange-2.3-samba-4.15.patch
 
 %description
 OpenChange provides libraries to access Microsoft Exchange servers
@@ -180,6 +181,7 @@ This package provides the server elements for OpenChange.
 %if !%{build_server_package}
 %patch20 -p1 -b .disable-server-reqs
 %endif
+%patch21 -p1 -b .samba-4.15
 
 %build
 # Backup manually-written Makefile
@@ -332,6 +334,9 @@ cp -r apidocs/html/libmapi++/* $RPM_BUILD_ROOT%{_datadir}/devhelp/books/openchan
 %endif
 
 %changelog
+* Mon Jul 19 2021 Milan Crha <mcrha@redhat.com> - 2.3-38
+- Add patch to build against samba 4.15
+
 * Thu Jun 17 2021 Milan Crha <mcrha@redhat.com> - 2.3-37
 - Avoid build time dependencies related to server, when it's not built