diff --git a/rust/config/global.go b/rust/config/global.go
index 68a74c2..7b79fca 100644
--- a/rust/config/global.go
+++ b/rust/config/global.go
@@ -15,6 +15,7 @@
 package config
 
 import (
+	"fmt"
 	"strings"
 
 	"android/soong/android"
@@ -93,6 +94,16 @@
 	}
 )
 
+func RustPath(ctx android.PathContext) string {
+	// I can't see any way to flatten the static variable inside Soong, so this
+	// reproduces the init logic.
+	var RustBase string = RustDefaultBase
+	if override := ctx.Config().Getenv("RUST_PREBUILTS_BASE"); override != "" {
+		RustBase = override
+	}
+	return fmt.Sprintf("%s/%s/%s", RustBase, HostPrebuiltTag(ctx.Config()), GetRustVersion(ctx))
+}
+
 func init() {
 	pctx.SourcePathVariable("RustDefaultBase", RustDefaultBase)
 	pctx.VariableConfigMethod("HostPrebuiltTag", HostPrebuiltTag)
diff --git a/rust/project_json.go b/rust/project_json.go
index 6cf492b..6e8cebe 100644
--- a/rust/project_json.go
+++ b/rust/project_json.go
@@ -19,6 +19,7 @@
 	"fmt"
 
 	"android/soong/android"
+	"android/soong/rust/config"
 )
 
 // This singleton collects Rust crate definitions and generates a JSON file
@@ -55,7 +56,8 @@
 }
 
 type rustProjectJson struct {
-	Crates []rustProjectCrate `json:"crates"`
+	Sysroot string             `json:"sysroot"`
+	Crates  []rustProjectCrate `json:"crates"`
 }
 
 // crateInfo is used during the processing to keep track of the known crates.
@@ -203,6 +205,8 @@
 		return
 	}
 
+	singleton.project.Sysroot = config.RustPath(ctx)
+
 	singleton.knownCrates = make(map[string]crateInfo)
 	ctx.VisitAllModules(func(module android.Module) {
 		singleton.appendCrateAndDependencies(ctx, module)