diff --git a/Cargo.toml b/Cargo.toml
index 7a179786..3d9e0d64 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,7 +20,7 @@ zlib, gzip, and raw deflate streams.
 members = ['systest']
 
 [dependencies]
-libc = "0.2.65"
+libc = { version = "0.2.65", optional = true }
 cfg-if = "1.0.0"
 miniz-sys = { path = "miniz-sys", version = "0.1.11", optional = true }
 libz-sys = { version = "1.1.0", optional = true, default-features = false }
@@ -37,8 +37,9 @@ quickcheck = { version = "1.0", default-features = false }
 
 [features]
 default = ["rust_backend"]
-any_zlib = [] # note: this is not a real user-facing feature
+any_zlib = ["libc"] # note: this is not a real user-facing feature
 zlib = ["any_zlib", "libz-sys"]
 zlib-ng-compat = ["zlib", "libz-sys/zlib-ng"]
 cloudflare_zlib = ["any_zlib", "cloudflare-zlib-sys"]
 rust_backend = ["miniz_oxide"]
+miniz-sys = ["dep:miniz-sys", "libc"]