diff --git a/rust/doc.go b/rust/doc.go
index fe3581b..6970d79 100644
--- a/rust/doc.go
+++ b/rust/doc.go
@@ -19,7 +19,7 @@
 )
 
 func init() {
-	android.RegisterSingletonType("rustdoc", RustdocSingleton)
+	android.RegisterParallelSingletonType("rustdoc", RustdocSingleton)
 }
 
 func RustdocSingleton() android.Singleton {
diff --git a/rust/project_json.go b/rust/project_json.go
index fe259d6..40aa7c7 100644
--- a/rust/project_json.go
+++ b/rust/project_json.go
@@ -74,7 +74,7 @@
 }
 
 func init() {
-	android.RegisterSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
+	android.RegisterParallelSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
 }
 
 // sourceProviderVariantSource returns the path to the source file if this
diff --git a/rust/rust.go b/rust/rust.go
index dc53cc0..4324ecb 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -45,7 +45,7 @@
 	})
 	pctx.Import("android/soong/rust/config")
 	pctx.ImportAs("cc_config", "android/soong/cc/config")
-	android.InitRegistrationContext.RegisterSingletonType("kythe_rust_extract", kytheExtractRustFactory)
+	android.InitRegistrationContext.RegisterParallelSingletonType("kythe_rust_extract", kytheExtractRustFactory)
 }
 
 type Flags struct {
diff --git a/rust/testing.go b/rust/testing.go
index 0a6a870..7f30569 100644
--- a/rust/testing.go
+++ b/rust/testing.go
@@ -200,8 +200,8 @@
 		ctx.BottomUp("rust_stdlinkage", LibstdMutator).Parallel()
 		ctx.BottomUp("rust_begin", BeginMutator).Parallel()
 	})
-	ctx.RegisterSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
-	ctx.RegisterSingletonType("kythe_rust_extract", kytheExtractRustFactory)
+	ctx.RegisterParallelSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
+	ctx.RegisterParallelSingletonType("kythe_rust_extract", kytheExtractRustFactory)
 	ctx.PostDepsMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.BottomUp("rust_sanitizers", rustSanitizerRuntimeMutator).Parallel()
 	})