diff --git a/master/custom/builders.py b/master/custom/builders.py
index f2d4812a..f0615e88 100644
--- a/master/custom/builders.py
+++ b/master/custom/builders.py
@@ -100,22 +100,23 @@
 
 # -- Stable Tier-2 builder ----------------------------------------------
 STABLE_BUILDERS_TIER_2 = [
-    # Linux x86-64 Clang
+    # Fedora Linux x86-64 Clang
     ("AMD64 Fedora Stable Clang", "cstratak-fedora-stable-x86_64", ClangUnixBuild),
     ("AMD64 Fedora Stable Clang Installed", "cstratak-fedora-stable-x86_64", ClangUnixInstalledBuild),
 
-    # Linux ppc64le GCC
+    # Fedora Linux ppc64le GCC
     ("PPC64LE Fedora Stable", "cstratak-fedora-stable-ppc64le", FedoraStableBuild),
     ("PPC64LE Fedora Stable Refleaks", "cstratak-fedora-stable-ppc64le", UnixRefleakBuild),
     ("PPC64LE Fedora Stable LTO", "cstratak-fedora-stable-ppc64le", LTONonDebugUnixBuild),
     ("PPC64LE Fedora Stable LTO + PGO", "cstratak-fedora-stable-ppc64le", LTOPGONonDebugBuild),
 
+    # RHEL8 ppc64le GCC
     ("PPC64LE RHEL8", "cstratak-RHEL8-ppc64le", RHEL8Build),
     ("PPC64LE RHEL8 Refleaks", "cstratak-RHEL8-ppc64le", UnixRefleakBuild),
     ("PPC64LE RHEL8 LTO", "cstratak-RHEL8-ppc64le", LTONonDebugUnixBuild),
     ("PPC64LE RHEL8 LTO + PGO", "cstratak-RHEL8-ppc64le", LTOPGONonDebugBuild),
 
-    # Linux aarch64 GCC/clang
+    # Fedora Linux aarch64 GCC/clang
     ("aarch64 Fedora Stable", "cstratak-fedora-stable-aarch64", FedoraStableBuild),
     ("aarch64 Fedora Stable Refleaks", "cstratak-fedora-stable-aarch64", UnixRefleakBuild),
     ("aarch64 Fedora Stable Clang", "cstratak-fedora-stable-aarch64", ClangUnixBuild),
@@ -123,6 +124,7 @@
     ("aarch64 Fedora Stable LTO", "cstratak-fedora-stable-aarch64", LTONonDebugUnixBuild),
     ("aarch64 Fedora Stable LTO + PGO", "cstratak-fedora-stable-aarch64", LTOPGONonDebugBuild),
 
+    # RHEL8 aarch64 GCC
     ("aarch64 RHEL8", "cstratak-RHEL8-aarch64", RHEL8Build),
     ("aarch64 RHEL8 Refleaks", "cstratak-RHEL8-aarch64", UnixRefleakBuild),
     ("aarch64 RHEL8 LTO", "cstratak-RHEL8-aarch64", LTONonDebugUnixBuild),
@@ -144,17 +146,27 @@
 # -- Stable Tier-3 builder ----------------------------------------------
 STABLE_BUILDERS_TIER_3 = [
 
-    # Linux s390x GCC
+    # Fedora Linux s390x GCC/Clang
+    ("s390x Fedora Stable", "cstratak-fedora-stable-s390x", UnixBuild),
+    ("s390x Fedora Stable Refleaks", "cstratak-fedora-stable-s390x", UnixRefleakBuild),
+    ("s390x Fedora Stable Clang", "cstratak-fedora-stable-s390x", ClangUnixBuild),
+    ("s390x Fedora Stable Clang Installed", "cstratak-fedora-stable-s390x", ClangUnixInstalledBuild),
+    ("s390x Fedora Stable LTO", "cstratak-fedora-stable-s390x", LTONonDebugUnixBuild),
+    ("s390x Fedora Stable LTO + PGO", "cstratak-fedora-stable-s390x", LTOPGONonDebugBuild),
+
+    # RHEL9 GCC
     ("s390x RHEL9", "cstratak-rhel9-s390x", UnixBuild),
     ("s390x RHEL9 Refleaks", "cstratak-rhel9-s390x", UnixRefleakBuild),
     ("s390x RHEL9 LTO", "cstratak-rhel9-s390x", LTONonDebugUnixBuild),
     ("s390x RHEL9 LTO + PGO", "cstratak-rhel9-s390x", LTOPGONonDebugBuild),
+
+    # RHEL8 GCC
     ("s390x RHEL8", "cstratak-rhel8-s390x", UnixBuild),
     ("s390x RHEL8 Refleaks", "cstratak-rhel8-s390x", UnixRefleakBuild),
     ("s390x RHEL8 LTO", "cstratak-rhel8-s390x", LTONonDebugUnixBuild),
     ("s390x RHEL8 LTO + PGO", "cstratak-rhel8-s390x", LTOPGONonDebugBuild),
 
-    # Linux ppc64le Clang
+    # Fedora Linux ppc64le Clang
     ("PPC64LE Fedora Stable Clang", "cstratak-fedora-stable-ppc64le", ClangUnixBuild),
     ("PPC64LE Fedora Stable Clang Installed", "cstratak-fedora-stable-ppc64le", ClangUnixInstalledBuild),
 
@@ -238,18 +250,20 @@
     ("AMD64 Fedora Rawhide Clang", "cstratak-fedora-rawhide-x86_64", ClangUnixBuild),
     ("AMD64 Fedora Rawhide Clang Installed", "cstratak-fedora-rawhide-x86_64", ClangUnixInstalledBuild),
 
-    # Linux ppc64le GCC
+    # Fedora Linux ppc64le GCC
     # Fedora Rawhide is unstable
     ("PPC64LE Fedora Rawhide", "cstratak-fedora-rawhide-ppc64le", FedoraRawhideBuild),
     ("PPC64LE Fedora Rawhide Refleaks", "cstratak-fedora-rawhide-ppc64le", UnixRefleakBuild),
     ("PPC64LE Fedora Rawhide LTO", "cstratak-fedora-rawhide-ppc64le", LTONonDebugUnixBuild),
     ("PPC64LE Fedora Rawhide LTO + PGO", "cstratak-fedora-rawhide-ppc64le", LTOPGONonDebugBuild),
 
+    # CentOS Stream 9 Linux ppc64le GCC
     ("PPC64LE CentOS9", "cstratak-CentOS9-ppc64le", CentOS9Build),
     ("PPC64LE CentOS9 Refleaks", "cstratak-CentOS9-ppc64le", UnixRefleakBuild),
     ("PPC64LE CentOS9 LTO", "cstratak-CentOS9-ppc64le", LTONonDebugUnixBuild),
     ("PPC64LE CentOS9 LTO + PGO", "cstratak-CentOS9-ppc64le", LTOPGONonDebugBuild),
 
+    # Fedora Linux aarch64 GCC/Clang
     # Fedora Rawhide is unstable
     ("aarch64 Fedora Rawhide", "cstratak-fedora-rawhide-aarch64", FedoraRawhideBuild),
     ("aarch64 Fedora Rawhide Refleaks", "cstratak-fedora-rawhide-aarch64", UnixRefleakBuild),
@@ -258,6 +272,7 @@
     ("aarch64 Fedora Rawhide LTO", "cstratak-fedora-rawhide-aarch64", LTONonDebugUnixBuild),
     ("aarch64 Fedora Rawhide LTO + PGO", "cstratak-fedora-rawhide-aarch64", LTOPGONonDebugBuild),
 
+    # CentOS Stream 9 Linux aarch64 GCC
     ("aarch64 CentOS9 Refleaks", "cstratak-CentOS9-aarch64", UnixRefleakBuild),
     ("aarch64 CentOS9 LTO", "cstratak-CentOS9-aarch64", LTONonDebugUnixBuild),
     ("aarch64 CentOS9 LTO + PGO", "cstratak-CentOS9-aarch64", LTOPGONonDebugBuild),
@@ -274,6 +289,14 @@
     ("PPC64LE Fedora Rawhide Clang", "cstratak-fedora-rawhide-ppc64le", ClangUnixBuild),
     ("PPC64LE Fedora Rawhide Clang Installed", "cstratak-fedora-rawhide-ppc64le", ClangUnixInstalledBuild),
 
+    # Linux s390x GCC/Clang
+    ("s390x Fedora Rawhide", "cstratak-fedora-rawhide-s390x", UnixBuild),
+    ("s390x Fedora Rawhide Refleaks", "cstratak-fedora-rawhide-s390x", UnixRefleakBuild),
+    ("s390x Fedora Rawhide Clang", "cstratak-fedora-rawhide-s390x", ClangUnixBuild),
+    ("s390x Fedora Rawhide Clang Installed", "cstratak-fedora-rawhide-s390x", ClangUnixInstalledBuild),
+    ("s390x Fedora Rawhide LTO", "cstratak-fedora-rawhide-s390x", LTONonDebugUnixBuild),
+    ("s390x Fedora Rawhide LTO + PGO", "cstratak-fedora-rawhide-s390x", LTOPGONonDebugBuild),
+
     # FreBSD x86-64 clang
     # FreeBSD 15 is CURRENT: development branch (at 2023-10-17)
     ("AMD64 FreeBSD15", "opsec-fbsd15", UnixBuild),
@@ -285,14 +308,16 @@
     # Linux x86-64 GCC musl
     ("AMD64 Alpine Linux", "ware-alpine", UnixBuild),
 
-    # Linux x86-64 GCC Fedora Rawhide Freethreading builders
+    # Linux GCC Fedora Rawhide Freethreading builders
     ("AMD64 Fedora Rawhide NoGIL", "cstratak-fedora-rawhide-x86_64", FedoraRawhideFreedthreadingBuild),
     ("aarch64 Fedora Rawhide NoGIL", "cstratak-fedora-rawhide-aarch64", FedoraRawhideFreedthreadingBuild),
     ("PPC64LE Fedora Rawhide NoGIL", "cstratak-fedora-rawhide-ppc64le", FedoraRawhideFreedthreadingBuild),
-    # Linux x86-64 GCC Fedora Rawhide Freethreading refleak builders
+    ("s390x Fedora Rawhide NoGIL", "cstratak-fedora-rawhide-s390x", FedoraRawhideFreedthreadingBuild),
+    # Linux GCC Fedora Rawhide Freethreading refleak builders
     ("AMD64 Fedora Rawhide NoGIL refleaks", "cstratak-fedora-rawhide-x86_64", UnixNoGilRefleakBuild),
     ("aarch64 Fedora Rawhide NoGIL refleaks", "cstratak-fedora-rawhide-aarch64", UnixNoGilRefleakBuild),
     ("PPC64LE Fedora Rawhide NoGIL refleaks", "cstratak-fedora-rawhide-ppc64le", UnixNoGilRefleakBuild),
+    ("s390x Fedora Rawhide NoGIL refleaks", "cstratak-fedora-rawhide-s390x", UnixNoGilRefleakBuild),
 
     # AIX ppc64
     ("PPC64 AIX", "edelsohn-aix-ppc64", AIXBuild),
diff --git a/master/custom/workers.py b/master/custom/workers.py
index fcf24bc3..d8433e8f 100644
--- a/master/custom/workers.py
+++ b/master/custom/workers.py
@@ -150,6 +150,16 @@ def get_workers(settings):
             not_branches=['3.9', '3.10', '3.11', '3.12', '3.13'],
             parallel_tests=4,
         ),
+        cpw(
+            name="cstratak-fedora-rawhide-s390x",
+            tags=['linux', 'unix', 'fedora', 's390x'],
+            parallel_tests=10,
+        ),
+        cpw(
+            name="cstratak-fedora-stable-s390x",
+            tags=['linux', 'unix', 'fedora', 's390x'],
+            parallel_tests=10,
+        ),
         cpw(
             name="cstratak-rhel8-s390x",
             tags=['linux', 'unix', 'rhel', 's390x'],