diff --git a/progenitor-impl/Cargo.toml b/progenitor-impl/Cargo.toml
index f0d31b8..963485f 100644
--- a/progenitor-impl/Cargo.toml
+++ b/progenitor-impl/Cargo.toml
@@ -9,7 +9,7 @@ description = "An OpenAPI client generator - core implementation"
 [dependencies]
 heck = "0.4.0"
 getopts = "0.2"
-indexmap = "1.8"
+indexmap = "1.9"
 openapiv3 = "1.0.0"
 proc-macro2 = "1.0"
 quote = "1.0"