diff --git a/libmimalloc-sys/Cargo.toml b/libmimalloc-sys/Cargo.toml
index 019da27..3337bab 100644
--- a/libmimalloc-sys/Cargo.toml
+++ b/libmimalloc-sys/Cargo.toml
@@ -12,6 +12,7 @@ links = "mimalloc"
 
 [dependencies]
 cty = { version = "0.2", optional = true }
+libc = "0.2"
 
 [build-dependencies]
 cc = "1.0"
diff --git a/libmimalloc-sys/src/lib.rs b/libmimalloc-sys/src/lib.rs
index e9d8027..ae9c550 100644
--- a/libmimalloc-sys/src/lib.rs
+++ b/libmimalloc-sys/src/lib.rs
@@ -3,6 +3,8 @@
 
 use core::ffi::c_void;
 
+extern crate libc;
+
 #[cfg(feature = "extended")]
 mod extended;
 #[cfg(feature = "extended")]