diff --git a/Cargo.toml b/Cargo.toml
index f417304..0a8e51a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,7 +33,7 @@ rustc_1_40 = []
 
 # features that require rustc 1.55
 # use const generics to implement Array for all array lengths
-rustc_1_55 = []
+rustc_1_55 = ["rustc_1_40"]
 
 # allow use of nightly feature `slice_partition_dedup`,
 # will become useless once that is stabilized: