diff --git a/ConfigureChecks.cmake b/ConfigureChecks.cmake
index 328292e699..786f35c0de 100644
--- a/ConfigureChecks.cmake
+++ b/ConfigureChecks.cmake
@@ -103,6 +103,10 @@ check_struct_has_member("struct tm"       tm_zone        time.h       HAVE_STRUC
 #Symbols but NOT enums or types
 check_symbol_exists(tzname "time.h" HAVE_TZNAME)
 
+# Types
+include(CheckTypeSize)
+check_type_size("ssize_t"       SSIZE_T)
+
 #
 # Check if the libc vsnprintf() conforms to C99. If this fails we may
 # need to fall-back on GLib I/O.
diff --git a/cmakeconfig.h.in b/cmakeconfig.h.in
index a9327993b0..d0deb679dc 100644
--- a/cmakeconfig.h.in
+++ b/cmakeconfig.h.in
@@ -294,10 +294,14 @@
 /* Note: not use in the code */
 #cmakedefine YYTEXT_POINTER
 
+/* Define to 1 if the 'ssize_t' type exists. */
+#cmakedefine HAVE_SSIZE_T 1
+
+#ifndef HAVE_SSIZE_T
+#  define ssize_t long int
+#endif
+
 #if defined(_MSC_VER)
-#  if !defined(QT_VERSION) || !defined(_SSIZE_T_DEFINED)
-   typedef int ssize_t;
-#  endif
 #  define strncasecmp strnicmp
 #  define popen       _popen
 #  define pclose      _pclose
diff --git a/epan/dissectors/packet-bpsec.c b/epan/dissectors/packet-bpsec.c
index 87fc0e1622..69a5901214 100644
--- a/epan/dissectors/packet-bpsec.c
+++ b/epan/dissectors/packet-bpsec.c
@@ -11,6 +11,8 @@
  *
  * SPDX-License-Identifier: LGPL-2.1-or-later
  */
+#include "config.h"
+
 #include "packet-bpsec.h"
 #include "packet-bpv7.h"
 #include <epan/packet.h>
diff --git a/epan/dissectors/packet-bpv7.c b/epan/dissectors/packet-bpv7.c
index d06b01e8f9..1b2d58a64a 100644
--- a/epan/dissectors/packet-bpv7.c
+++ b/epan/dissectors/packet-bpv7.c
@@ -11,6 +11,8 @@
  *
  * SPDX-License-Identifier: LGPL-2.1-or-later
  */
+#include "config.h"
+
 #include "packet-bpv7.h"
 #include "epan/wscbor.h"
 #include <epan/packet.h>
diff --git a/epan/dissectors/packet-btmesh-beacon.c b/epan/dissectors/packet-btmesh-beacon.c
index 0e929b696d..4c33173598 100644
--- a/epan/dissectors/packet-btmesh-beacon.c
+++ b/epan/dissectors/packet-btmesh-beacon.c
@@ -13,6 +13,8 @@
  * https://www.bluetooth.com/specifications/mesh-specifications
  */
 
+#include "config.h"
+
 #include <epan/packet.h>
 #include <epan/prefs.h>
 #include <epan/expert.h>
diff --git a/epan/dissectors/packet-btmesh-pbadv.c b/epan/dissectors/packet-btmesh-pbadv.c
index 6ef16f6e92..5bd55c494e 100644
--- a/epan/dissectors/packet-btmesh-pbadv.c
+++ b/epan/dissectors/packet-btmesh-pbadv.c
@@ -13,6 +13,8 @@
  * https://www.bluetooth.com/specifications/mesh-specifications
  */
 
+#include "config.h"
+
 #include <epan/packet.h>
 #include <epan/prefs.h>
 #include <epan/reassemble.h>
diff --git a/epan/dissectors/packet-btmesh-provisioning.c b/epan/dissectors/packet-btmesh-provisioning.c
index 802cf9963b..ebce68acd9 100644
--- a/epan/dissectors/packet-btmesh-provisioning.c
+++ b/epan/dissectors/packet-btmesh-provisioning.c
@@ -13,6 +13,8 @@
  * https://www.bluetooth.com/specifications/mesh-specifications
  */
 
+#include "config.h"
+
 #include <epan/packet.h>
 #include <epan/prefs.h>
 #include <epan/expert.h>
diff --git a/epan/dissectors/packet-btmesh-proxy.c b/epan/dissectors/packet-btmesh-proxy.c
index 6a690e3620..7d0787ed83 100644
--- a/epan/dissectors/packet-btmesh-proxy.c
+++ b/epan/dissectors/packet-btmesh-proxy.c
@@ -13,6 +13,8 @@
  * https://www.bluetooth.com/specifications/mesh-specifications
  */
 
+#include "config.h"
+
 #include <epan/packet.h>
 #include <epan/prefs.h>
 #include <epan/reassemble.h>
diff --git a/epan/dissectors/packet-cemi.c b/epan/dissectors/packet-cemi.c
index 3ef9daf575..c3741b8fea 100644
--- a/epan/dissectors/packet-cemi.c
+++ b/epan/dissectors/packet-cemi.c
@@ -10,6 +10,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include <epan/packet.h>
 #include "packet-knxip.h"
 
diff --git a/epan/dissectors/packet-knxip.c b/epan/dissectors/packet-knxip.c
index cd82fa2060..f4e715ceea 100644
--- a/epan/dissectors/packet-knxip.c
+++ b/epan/dissectors/packet-knxip.c
@@ -18,6 +18,8 @@
  * for the specifications.
  */
 
+#include "config.h"
+
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/epan/dissectors/packet-knxip_decrypt.c b/epan/dissectors/packet-knxip_decrypt.c
index ccf93b0be7..4eaba15a04 100644
--- a/epan/dissectors/packet-knxip_decrypt.c
+++ b/epan/dissectors/packet-knxip_decrypt.c
@@ -9,6 +9,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #define WS_LOG_DOMAIN "packet-knxip"
 
 #include <wsutil/file_util.h>
diff --git a/epan/dissectors/packet-tpm20.c b/epan/dissectors/packet-tpm20.c
index f4e665f6eb..f3a9ec4f70 100644
--- a/epan/dissectors/packet-tpm20.c
+++ b/epan/dissectors/packet-tpm20.c
@@ -10,6 +10,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include <stdbool.h>
 #include <epan/packet.h>
 #include <epan/to_str.h>
diff --git a/epan/tvbuff_rdp.c b/epan/tvbuff_rdp.c
index ee7832360c..8487df384b 100644
--- a/epan/tvbuff_rdp.c
+++ b/epan/tvbuff_rdp.c
@@ -8,6 +8,8 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
+#include "config.h"
+
 #include <glib.h>
 #include <stdbool.h>
 
diff --git a/epan/wscbor.c b/epan/wscbor.c
index ac250fa2fc..3e839ef741 100644
--- a/epan/wscbor.c
+++ b/epan/wscbor.c
@@ -11,6 +11,7 @@
  *
  * SPDX-License-Identifier: LGPL-2.1-or-later
  */
+#include "config.h"
 
 #include <epan/packet.h>
 #include <epan/exceptions.h>
diff --git a/file_packet_provider.c b/file_packet_provider.c
index c9ca08e7e3..1b92eebca0 100644
--- a/file_packet_provider.c
+++ b/file_packet_provider.c
@@ -7,6 +7,7 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
+#include "config.h"
 
 #include <glib.h>
 
diff --git a/plugins/epan/mate/mate_grammar.lemon b/plugins/epan/mate/mate_grammar.lemon
index 0947afa2e5..73b320d8d6 100644
--- a/plugins/epan/mate/mate_grammar.lemon
+++ b/plugins/epan/mate/mate_grammar.lemon
@@ -19,6 +19,7 @@
 #ifndef NDEBUG
 #define NDEBUG
 #endif
+#include "config.h"
 
 #include "mate.h"
 #include "mate_grammar.h"
diff --git a/ui/qt/capture_file_dialog.cpp b/ui/qt/capture_file_dialog.cpp
index bb56b7b2be..e8715bebad 100644
--- a/ui/qt/capture_file_dialog.cpp
+++ b/ui/qt/capture_file_dialog.cpp
@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include "file.h"
 
 #include <wiretap/wtap.h>
diff --git a/ui/qt/rtp_player_dialog.cpp b/ui/qt/rtp_player_dialog.cpp
index 6e5f5f9160..d4dec83638 100644
--- a/ui/qt/rtp_player_dialog.cpp
+++ b/ui/qt/rtp_player_dialog.cpp
@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include <ui/rtp_media.h>
 #include <ui/tap-rtp-common.h>
 #include "rtp_player_dialog.h"
diff --git a/ui/qt/utils/frame_information.cpp b/ui/qt/utils/frame_information.cpp
index ef0b849564..d344bc0403 100644
--- a/ui/qt/utils/frame_information.cpp
+++ b/ui/qt/utils/frame_information.cpp
@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include <epan/epan_dissect.h>
 #include "epan/epan.h"
 #include "epan/column.h"
diff --git a/ui/qt/widgets/wireshark_file_dialog.cpp b/ui/qt/widgets/wireshark_file_dialog.cpp
index 332d394e7c..acf9c7db50 100644
--- a/ui/qt/widgets/wireshark_file_dialog.cpp
+++ b/ui/qt/widgets/wireshark_file_dialog.cpp
@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include "config.h"
+
 #include "wireshark_file_dialog.h"
 
 #ifdef Q_OS_WIN
diff --git a/wsutil/regex.c b/wsutil/regex.c
index 86ce6625a3..83caa96291 100644
--- a/wsutil/regex.c
+++ b/wsutil/regex.c
@@ -83,7 +83,7 @@ ws_regex_compile(const char *patt, char **errmsg)
 
 
 static bool
-match_pcre2(pcre2_code *code, const char *subj, gssize subj_size)
+match_pcre2(pcre2_code *code, const char *subj, ssize_t subj_size)
 {
     PCRE2_SIZE length;
     pcre2_match_data *match_data;
@@ -123,7 +123,7 @@ match_pcre2(pcre2_code *code, const char *subj, gssize subj_size)
 
 
 bool
-ws_regex_matches(const ws_regex_t *re, const char *subj, gssize subj_size)
+ws_regex_matches(const ws_regex_t *re, const char *subj, ssize_t subj_size)
 {
     ws_return_val_if_null(re, FALSE);
     ws_return_val_if_null(subj, FALSE);
diff --git a/wsutil/regex.h b/wsutil/regex.h
index 9f5803a085..12c7cffe80 100644
--- a/wsutil/regex.h
+++ b/wsutil/regex.h
@@ -23,7 +23,7 @@ WS_DLL_PUBLIC ws_regex_t *
 ws_regex_compile(const char *patt, char **errmsg);
 
 WS_DLL_PUBLIC bool
-ws_regex_matches(const ws_regex_t *re, const char *subj, gssize subj_size);
+ws_regex_matches(const ws_regex_t *re, const char *subj, ssize_t subj_size);
 
 WS_DLL_PUBLIC void
 ws_regex_free(ws_regex_t *re);