diff --git a/Cargo.toml b/Cargo.toml
index 04b0145c..e71cd054 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ edition = "2018"
 
 [dependencies]
 cortex-m = "0.7.7"
+critical-section = { version = "1.1.2", optional = true }
 vcell = "0.1.3"
 
 [dependencies.cortex-m-rt]