diff --git a/Cargo.toml b/Cargo.toml
index 60f50f8908959e57cc18d64112938776125d1bd2..e4c92d2e179e8cf818d09d4f43459ec4544857ee 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,12 +9,12 @@ version = "0.3.0"
 
 [dependencies]
 bare-metal = "0.2.0"
-cortex-m = "0.5.0"
+cortex-m = "0.4.0"
 vcell = "0.1.0"
 
 [dependencies.cortex-m-rt]
 optional = true
-version = "0.5.0"
+version = "0.4.0"
 
 [features]
 rt = ["cortex-m-rt/device"]
\ No newline at end of file