diff --git a/Cargo.lock b/Cargo.lock
index 015c0fe1be1..e6069cc4b99 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4341,7 +4341,6 @@ dependencies = [
 name = "rustc_session"
 version = "0.0.0"
 dependencies = [
- "bitflags",
  "getopts",
  "num_cpus",
  "rustc_ast",
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index 4c72920502f..571fd581d3f 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -5,7 +5,6 @@ version = "0.0.0"
 edition = "2018"
 
 [dependencies]
-bitflags = "1.2.1"
 getopts = "0.2"
 rustc_macros = { path = "../rustc_macros" }
 tracing = "0.1"