diff --git a/extra/firefox/build b/extra/firefox/build
index 7dc20c37..943153b7 100755
--- a/extra/firefox/build
+++ b/extra/firefox/build
@@ -2,6 +2,18 @@
 
 patch -p1 < no-x11.patch
 
+# Firefox 90 cannot be built with rust 1.54.0. This updates a crate
+# used by Firefox to work around this issue.
+{
+    sed '/const_fn,/d' third_party/rust/packed_simd/src/lib.rs > _
+    mv -f _ third_party/rust/packed_simd/src/lib.rs
+
+    printf '{"package":null,"files":{}}\n' \
+        > third_party/rust/packed_simd/.cargo-checksum.json
+
+    patch -p1 < rust-1.45.0.patch
+}
+
 # Remove fribidi dependency.
 sed '/fribidi/d' config/system-headers.mozbuild > _
 mv -f _ config/system-headers.mozbuild
diff --git a/extra/firefox/checksums b/extra/firefox/checksums
index eb5c3f86..45be3dc0 100644
--- a/extra/firefox/checksums
+++ b/extra/firefox/checksums
@@ -3,3 +3,4 @@ f0611136bee505811e9ca11ca7ac188ef5323a8e2ef19cffd3edb3cf08fd791e
 3dce6601b495f5b3d45b59f7d2492a340ee7e84b5beca17e48f862502bd5603f
 f0e8bb1f9b7eb0b01285495a2699df3a4b766784c1765a8f1aeedf63c0806369
 a88ecf15a164dd82f9deb6576ff744d4ed1fda7ebd273e63b01e0c1d93c9ed1d
+8346ee5ef1aa1aea53d76d50044af84f7a26468fd1fa7e9f7a0d5819ed4d81bb
diff --git a/extra/firefox/patches/rust-1.45.0.patch b/extra/firefox/patches/rust-1.45.0.patch
new file mode 100644
index 00000000..653635b1
--- /dev/null
+++ b/extra/firefox/patches/rust-1.45.0.patch
@@ -0,0 +1,269 @@
+From 728d47506fe3a2599818060bd6e02e4bd3e338d5 Mon Sep 17 00:00:00 2001
+From: Jubilee Young <workingjubilee@gmail.com>
+Date: Sat, 15 May 2021 20:15:42 -0700
+Subject: [PATCH] Update shuffle API for const generics
+
+---
+ src/api/shuffle.rs  |  46 +++++++++----------
+ src/codegen/llvm.rs | 109 ++++++++++++++++++++++++++------------------
+ src/lib.rs          |   3 ++
+ 3 files changed, 90 insertions(+), 68 deletions(-)
+
+diff --git a/third_party/rust/packed_simd/src/api/shuffle.rs b/src/api/shuffle.rs
+index da80b912..fda29ccd 100644
+--- a/third_party/rust/packed_simd/src/api/shuffle.rs
++++ b/third_party/rust/packed_simd/src/api/shuffle.rs
+@@ -75,20 +75,18 @@ macro_rules! shuffle {
+     ($vec0:expr, $vec1:expr, [$l0:expr, $l1:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector2(
++            $crate::Simd($crate::__shuffle_vector2::<{[$l0, $l1]}, _, _>(
+                 $vec0.0,
+                 $vec1.0,
+-                [$l0, $l1],
+             ))
+         }
+     }};
+     ($vec0:expr, $vec1:expr, [$l0:expr, $l1:expr, $l2:expr, $l3:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector4(
++            $crate::Simd($crate::__shuffle_vector4::<{[$l0, $l1, $l2, $l3]}, _, _>(
+                 $vec0.0,
+                 $vec1.0,
+-                [$l0, $l1, $l2, $l3],
+             ))
+         }
+     }};
+@@ -97,10 +95,9 @@ macro_rules! shuffle {
+       $l4:expr, $l5:expr, $l6:expr, $l7:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector8(
++            $crate::Simd($crate::__shuffle_vector8::<{[$l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7]}, _, _>(
+                 $vec0.0,
+                 $vec1.0,
+-                [$l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7],
+             ))
+         }
+     }};
+@@ -111,13 +108,14 @@ macro_rules! shuffle {
+       $l12:expr, $l13:expr, $l14:expr, $l15:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector16(
+-                $vec0.0,
+-                $vec1.0,
++            $crate::Simd($crate::__shuffle_vector16::<{
+                 [
+                     $l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7, $l8, $l9, $l10,
+                     $l11, $l12, $l13, $l14, $l15,
+-                ],
++                ]
++            }, _, _>(
++                $vec0.0,
++                $vec1.0,
+             ))
+         }
+     }};
+@@ -132,15 +130,16 @@ macro_rules! shuffle {
+       $l28:expr, $l29:expr, $l30:expr, $l31:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector32(
+-                $vec0.0,
+-                $vec1.0,
++            $crate::Simd($crate::__shuffle_vector32::<{
+                 [
+                     $l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7, $l8, $l9, $l10,
+                     $l11, $l12, $l13, $l14, $l15, $l16, $l17, $l18, $l19,
+                     $l20, $l21, $l22, $l23, $l24, $l25, $l26, $l27, $l28,
+                     $l29, $l30, $l31,
+-                ],
++                ]
++            }, _, _>(
++                $vec0.0,
++                $vec1.0,
+             ))
+         }
+     }};
+@@ -163,18 +162,17 @@ macro_rules! shuffle {
+       $l60:expr, $l61:expr, $l62:expr, $l63:expr]) => {{
+         #[allow(unused_unsafe)]
+         unsafe {
+-            $crate::Simd($crate::__shuffle_vector64(
++            $crate::Simd($crate::__shuffle_vector64::<{[
++                $l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7, $l8, $l9, $l10,
++                $l11, $l12, $l13, $l14, $l15, $l16, $l17, $l18, $l19,
++                $l20, $l21, $l22, $l23, $l24, $l25, $l26, $l27, $l28,
++                $l29, $l30, $l31, $l32, $l33, $l34, $l35, $l36, $l37,
++                $l38, $l39, $l40, $l41, $l42, $l43, $l44, $l45, $l46,
++                $l47, $l48, $l49, $l50, $l51, $l52, $l53, $l54, $l55,
++                $l56, $l57, $l58, $l59, $l60, $l61, $l62, $l63,
++            ]}, _, _>(
+                 $vec0.0,
+                 $vec1.0,
+-                [
+-                    $l0, $l1, $l2, $l3, $l4, $l5, $l6, $l7, $l8, $l9, $l10,
+-                    $l11, $l12, $l13, $l14, $l15, $l16, $l17, $l18, $l19,
+-                    $l20, $l21, $l22, $l23, $l24, $l25, $l26, $l27, $l28,
+-                    $l29, $l30, $l31, $l32, $l33, $l34, $l35, $l36, $l37,
+-                    $l38, $l39, $l40, $l41, $l42, $l43, $l44, $l45, $l46,
+-                    $l47, $l48, $l49, $l50, $l51, $l52, $l53, $l54, $l55,
+-                    $l56, $l57, $l58, $l59, $l60, $l61, $l62, $l63,
+-                ],
+             ))
+         }
+      }};
+diff --git a/third_party/rust/packed_simd/src/codegen/llvm.rs b/src/codegen/llvm.rs
+index 93c6ce6b..52b11a95 100644
+--- a/third_party/rust/packed_simd/src/codegen/llvm.rs
++++ b/third_party/rust/packed_simd/src/codegen/llvm.rs
+@@ -7,52 +7,73 @@ use crate::sealed::Simd;
+
+ // Shuffle intrinsics: expanded in users' crates, therefore public.
+ extern "platform-intrinsic" {
+-    // FIXME: Passing this intrinsics an `idx` array with an index that is
+-    // out-of-bounds will produce a monomorphization-time error.
+-    // https://github.com/rust-lang-nursery/packed_simd/issues/21
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle2<T, U>(x: T, y: T, idx: [u32; 2]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 2], Output = U>;
+-
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle4<T, U>(x: T, y: T, idx: [u32; 4]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 4], Output = U>;
+-
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle8<T, U>(x: T, y: T, idx: [u32; 8]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 8], Output = U>;
+-
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle16<T, U>(x: T, y: T, idx: [u32; 16]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 16], Output = U>;
+-
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle32<T, U>(x: T, y: T, idx: [u32; 32]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 32], Output = U>;
+-
+-    #[rustc_args_required_const(2)]
+-    pub fn simd_shuffle64<T, U>(x: T, y: T, idx: [u32; 64]) -> U
+-    where
+-        T: Simd,
+-        <T as Simd>::Element: Shuffle<[u32; 64], Output = U>;
++    pub fn simd_shuffle2<T, U>(x: T, y: T, idx: [u32; 2]) -> U;
++    pub fn simd_shuffle4<T, U>(x: T, y: T, idx: [u32; 4]) -> U;
++    pub fn simd_shuffle8<T, U>(x: T, y: T, idx: [u32; 8]) -> U;
++    pub fn simd_shuffle16<T, U>(x: T, y: T, idx: [u32; 16]) -> U;
++    pub fn simd_shuffle32<T, U>(x: T, y: T, idx: [u32; 32]) -> U;
++    pub fn simd_shuffle64<T, U>(x: T, y: T, idx: [u32; 64]) -> U;
+ }
+
+-pub use self::simd_shuffle16 as __shuffle_vector16;
+-pub use self::simd_shuffle2 as __shuffle_vector2;
+-pub use self::simd_shuffle32 as __shuffle_vector32;
+-pub use self::simd_shuffle4 as __shuffle_vector4;
+-pub use self::simd_shuffle64 as __shuffle_vector64;
+-pub use self::simd_shuffle8 as __shuffle_vector8;
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector2<const IDX: [u32; 2], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 2], Output = U>,
++{
++    simd_shuffle2(x, y, IDX)
++}
++
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector4<const IDX: [u32; 4], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 4], Output = U>,
++{
++    simd_shuffle4(x, y, IDX)
++}
++
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector8<const IDX: [u32; 8], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 8], Output = U>,
++{
++    simd_shuffle8(x, y, IDX)
++}
++
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector16<const IDX: [u32; 16], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 16], Output = U>,
++{
++    simd_shuffle16(x, y, IDX)
++}
++
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector32<const IDX: [u32; 32], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 32], Output = U>,
++{
++    simd_shuffle32(x, y, IDX)
++}
++
++#[allow(clippy::missing_safety_doc)]
++#[inline]
++pub unsafe fn __shuffle_vector64<const IDX: [u32; 64], T, U>(x: T, y: T) -> U
++where
++    T: Simd,
++    <T as Simd>::Element: Shuffle<[u32; 64], Output = U>,
++{
++    simd_shuffle64(x, y, IDX)
++}
+
+ extern "platform-intrinsic" {
+     crate fn simd_eq<T, U>(x: T, y: T) -> U;
+diff --git a/third_party/rust/packed_simd/src/lib.rs
+b/third_party/rust/packed_simd/src/lib.rs
+index 9c9b060..cccdb85 100644
+--- a/third_party/rust/packed_simd/src/lib.rs
++++ b/third_party/rust/packed_simd/src/lib.rs
+@@ -200,6 +200,7 @@
+ //!   preserving, etc.
+
+ #![feature(
++    const_generics,
+     repr_simd,
+     rustc_attrs,
+     platform_intrinsics,
+@@ -216,6 +217,7 @@
+         // FIXME: these types are unsound in C FFI already
+         // See https://github.com/rust-lang/rust/issues/53346
+         improper_ctypes_definitions,
++        incomplete_features,
+         clippy::cast_possible_truncation,
+         clippy::cast_lossless,
+         clippy::cast_possible_wrap,
+@@ -226,6 +228,7 @@
+         // See https://github.com/rust-lang/rust-clippy/issues/3410
+         clippy::use_self,
+         clippy::wrong_self_convention,
++        clippy::from_over_into,
+ )]
+ #![cfg_attr(test, feature(hashmap_internals))]
+ #![deny(rust_2018_idioms, clippy::missing_inline_in_public_items)]
diff --git a/extra/firefox/sources b/extra/firefox/sources
index 7bc51104..f87b0daa 100644
--- a/extra/firefox/sources
+++ b/extra/firefox/sources
@@ -3,3 +3,4 @@ https://ftp.gnu.org/gnu/autoconf/autoconf-2.13.tar.gz autoconf2.13/
 https://github.com/yasm/yasm/releases/download/v1.3.0/yasm-1.3.0.tar.gz yasm
 https://fossies.org/linux/misc/zip30.tar.gz zip
 patches/no-x11.patch
+patches/rust-1.45.0.patch