diff --git a/mail/thunderbird/files/patch-third__party_xsimd_include_xsimd_types_xsimd__vsx__register.hpp b/mail/thunderbird/files/patch-third__party_xsimd_include_xsimd_types_xsimd__vsx__register.hpp
new file mode 100644
index 000000000000..51367c0ea805
--- /dev/null
+++ b/mail/thunderbird/files/patch-third__party_xsimd_include_xsimd_types_xsimd__vsx__register.hpp
@@ -0,0 +1,16 @@
+--- third_party/xsimd/include/xsimd/types/xsimd_vsx_register.hpp.orig	2026-06-28 10:55:46.683534000 +0200
++++ third_party/xsimd/include/xsimd/types/xsimd_vsx_register.hpp	2026-06-28 10:55:46.694422000 +0200
+@@ -64,10 +64,10 @@
+         XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(short, short);
+         XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(unsigned int, int);
+         XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(int, int);
+-        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(unsigned long, long);
+-        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(long, long);
++        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(unsigned long, long long);
++        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(long, long long);
+         XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(float, int);
+-        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(double, long);
++        XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER(double, long long);
+ 
+ #undef XSIMD_DECLARE_SIMD_BOOL_VSX_REGISTER
+     }