diff --git a/deps/rust/Cargo.lock b/deps/rust/Cargo.lock
index d50a4daf1c4..09cc2de5c34 100644
--- a/deps/rust/Cargo.lock
+++ b/deps/rust/Cargo.lock
@@ -633,6 +633,7 @@ dependencies = [
  "httpdate",
  "hyper",
  "hyper-util",
+ "icu_calendar",
  "ipnet",
  "libc",
  "libm",
@@ -1114,15 +1115,15 @@ dependencies = [
 
 [[package]]
 name = "icu_calendar"
-version = "2.3.0"
+version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58655df2f728e46e4eee80bddebefacf52ec3e77cdb925014b47c5a5905eb55c"
+checksum = "a2b2acc6263f494f1df50685b53ff8e57869e47d5c6fe39c23d518ae9a4f3e45"
 dependencies = [
  "calendrical_calculations",
  "displaydoc",
  "icu_calendar_data",
+ "icu_locale",
  "icu_locale_core",
- "icu_locale_fallback",
  "icu_provider",
  "tinystr",
  "zerovec",
@@ -1130,15 +1131,15 @@ dependencies = [
 
 [[package]]
 name = "icu_calendar_data"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc00caaa3fb3201ff7a18aa458e8c3ab042b9da154cfdf948bdde3936c31c36e"
+checksum = "118577bcf3a0fa7c6ac0a7d6e951814da84ee56b9b1f68fb4d8d10b08cefaf4d"
 
 [[package]]
 name = "icu_collections"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa68d21081c4a05d5a901a1c62add574c77048b6a1c67be3b50ce0b60d4ca513"
+checksum = "2984d1cd16c883d7935b9e07e44071dca8d917fd52ecc02c04d5fa0b5a3f191c"
 dependencies = [
  "displaydoc",
  "potential_utf",
@@ -1149,44 +1150,45 @@ dependencies = [
 ]
 
 [[package]]
-name = "icu_locale_core"
-version = "2.3.0"
+name = "icu_locale"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d56e28588da92eee5c3201a6eff33fabdd49b62269c8938d4ff050ce4d900deb"
+checksum = "d5a396343c7208121dc86e35623d3dfe19814a7613cfd14964994cdc9c9a2e26"
 dependencies = [
- "displaydoc",
- "litemap",
- "serde",
+ "icu_collections",
+ "icu_locale_core",
+ "icu_locale_data",
+ "icu_provider",
+ "potential_utf",
  "tinystr",
- "writeable",
  "zerovec",
 ]
 
 [[package]]
-name = "icu_locale_fallback"
+name = "icu_locale_core"
 version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "251af8e57c9400e3eb58242fe5b8b1152b2a64fdf4cf632f923c38ccee6f2fa9"
+checksum = "d56e28588da92eee5c3201a6eff33fabdd49b62269c8938d4ff050ce4d900deb"
 dependencies = [
- "icu_locale_core",
- "icu_locale_fallback_data",
- "icu_provider",
- "potential_utf",
+ "displaydoc",
+ "litemap",
+ "serde",
  "tinystr",
+ "writeable",
  "zerovec",
 ]
 
 [[package]]
-name = "icu_locale_fallback_data"
-version = "2.3.0"
+name = "icu_locale_data"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "decf2a22ec8fa68f1a0c1129a3f8583f8f8bc24e8b9ccbe98ead99f62a4dc3a8"
+checksum = "d5fdcc9ac77c6d74ff5cf6e65ef3181d6af32003b16fce3a77fb451d2f695993"
 
 [[package]]
 name = "icu_normalizer"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "12f9cf5f235641ed274641dd81c3f28d870e276763d0797aeeab72317b1c646f"
+checksum = "c56e5ee99d6e3d33bd91c5d85458b6005a22140021cc324cea84dd0e72cff3b4"
 dependencies = [
  "icu_collections",
  "icu_normalizer_data",
@@ -1198,17 +1200,16 @@ dependencies = [
 
 [[package]]
 name = "icu_normalizer_data"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1563da1ed3e0b3bf3d74c9b85917ac9c56464d2f57242270c09c9e752f8021a0"
+checksum = "da3be0ae77ea334f4da67c12f149704f19f81d1adf7c51cf482943e84a2bad38"
 
 [[package]]
 name = "icu_properties"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7e7ca276ad3145661a65914e6daf131ca5120cd3dcee8f8f3214b8875184a148"
+checksum = "bee3b67d0ea5c2cca5003417989af8996f8604e34fb9ddf96208a033901e70de"
 dependencies = [
- "displaydoc",
  "icu_collections",
  "icu_locale_core",
  "icu_properties_data",
@@ -1219,9 +1220,9 @@ dependencies = [
 
 [[package]]
 name = "icu_properties_data"
-version = "2.3.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e590f038c1464a96894fd6d10127e90a8be4509f56ff7ecef851b15cee0b7caa"
+checksum = "8e2bbb201e0c04f7b4b3e14382af113e17ba4f63e2c9d2ee626b720cbce54a14"
 
 [[package]]
 name = "icu_provider"
diff --git a/deps/rust/Cargo.toml b/deps/rust/Cargo.toml
index 8a46acbffc7..4eeeedc0d80 100644
--- a/deps/rust/Cargo.toml
+++ b/deps/rust/Cargo.toml
@@ -96,6 +96,9 @@ serde = { version = "1", features = ["derive"] }
 # the versions of these and other exact pins in temporal_capi's dependency tree.
 temporal_capi = { version = "=0.2.6", features = ["zoneinfo64"] }
 temporal_rs = { version = "=0.2.6", default-features = false, features = ["float64_representable_durations"] }
+# temporal_rs accepts a newer icu_calendar than Chromium builds it with, and Cargo cannot
+# downgrade it without moving the other ICU4X crates that share its version line.
+icu_calendar = { version = "=2.2.1", default-features = false }
 thiserror = "2"
 tower-service = "0.3"
 # tokio is huge, let's enable only features when we actually need them.