diff --git a/Cargo.toml b/Cargo.toml
index 7222bd75f..795f679fb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,7 +14,7 @@ rust-version = "1.36"
 
 [dependencies]
 serde = { version = "1.0.100", default-features = false }
-indexmap = { version = "1.5", optional = true }
+indexmap = { version = "1.5.2", features = ["std"], optional = true }
 itoa = "1.0"
 ryu = "1.0"