diff --git a/core/http/Cargo.toml b/core/http/Cargo.toml
index c43cd0c9..a23a897e 100644
--- a/core/http/Cargo.toml
+++ b/core/http/Cargo.toml
@@ -23,7 +23,7 @@ smallvec = "1.0"
 percent-encoding = "1"
 hyper = { version = "0.10.13", default-features = false }
 time = "0.1"
-indexmap = "1.0"
+indexmap = { version = "1.5.2", features = ["std"] }
 rustls = { version = "0.14", optional = true }
 state = "0.4"
 cookie = { version = "0.11.3", features = ["percent-encode"] }