diff --git a/Cargo.toml b/Cargo.toml
index 44e7a7e..bdf201c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,7 +35,7 @@ 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"]
 
 # features that require rustc 1.57
 # add try_reserve functions to types that heap allocate.
@@ -43,7 +43,7 @@ rustc_1_57 = ["rustc_1_55"]
 
 # features that require rustc 1.61
 # add retain_mut function to TinyVec
-rustc_1_61 = []
+rustc_1_61 = ["rustc_1_57"]
 
 # allow use of nightly feature `slice_partition_dedup`,
 # will become useless once that is stabilized: