diff --git a/profiles/package.mask b/profiles/package.mask
index 0f1c27b20895c..776dda86d18e8 100644
--- a/profiles/package.mask
+++ b/profiles/package.mask
@@ -33,6 +33,12 @@
 
 #--- END OF EXAMPLES ---
 
+# Sam James <sam@gentoo.org> (2024-12-07)
+# Breaks Mozilla's build system `mach`: bug #945882, bug #945857, and bug #946002.
+# Upstream bug is at https://bugzilla.mozilla.org/show_bug.cgi?id=1935621.
+=dev-lang/python-3.12.8
+=dev-lang/python-3.13.1
+
 # Michał Górny <mgorny@gentoo.org> (2024-12-05)
 # 6.12.2 does not boot for me.
 =sys-kernel/gentoo-kernel-6.12.2