diff --git a/Cargo.toml b/Cargo.toml
index ea63a2e..af16166 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,5 +16,7 @@ serde_json = "0.9"
 serde_derive = "0.9"
 
 [dependencies.chrono]
-version = "0.3"
+# Locked to 0.3.0 since chrono 0.3.1 uses serde ^1, which is incompatible
+# with serde 0.9 specified above.
+version = "=0.3.0"
 features = ["serde"]