diff --git a/rust/hg-core/Cargo.toml b/rust/hg-core/Cargo.toml
--- a/rust/hg-core/Cargo.toml
+++ b/rust/hg-core/Cargo.toml
@@ -38,7 +38,7 @@ zstd = "0.5.3"
 format-bytes = "0.3.0"
 # once_cell 1.15 uses edition 2021, while the heptapod CI
 # uses an old version of Cargo that doesn't support it.
-once_cell = "=1.14.0"
+once_cell = "1.14.0"
 
 # We don't use the `miniz-oxide` backend to not change rhg benchmarks and until
 # we have a clearer view of which backend is the fastest.