diff --git a/snafu-derive/Cargo.toml b/snafu-derive/Cargo.toml
index e3127ef..d729bf6 100644
--- a/snafu-derive/Cargo.toml
+++ b/snafu-derive/Cargo.toml
@@ -22,4 +22,4 @@ proc-macro = true
 syn = { version = "2.0", features = ["full"] }
 quote = "1.0.25"
 proc-macro2 = "1.0.52"
-heck = "0.4"
+heck = { version = ">= 0.4, < 0.6", default-features = false }