diff --git a/src/lib.rs b/src/lib.rs
index 8a95877..b389693 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,7 +9,7 @@
 #[cfg(feature="format")] extern crate pad;
 #[cfg(feature="parse")]  extern crate iso8601;
 
-#[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "redox")))]
+#[cfg(all(any(unix, target_os = "wasi"), not(target_os = "macos"), not(target_os = "ios"), not(target_os = "redox")))]
 extern crate libc;  // used in the system module
 
 #[cfg(windows)] extern crate winapi;
diff --git a/src/system.rs b/src/system.rs
index f69a4aa..8fb6ffd 100644
--- a/src/system.rs
+++ b/src/system.rs
@@ -16,7 +16,7 @@ extern {
     fn gettimeofday(tp: *mut libc::timeval, tzp: *mut libc::timezone) -> libc::c_int;
 }
 
-#[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "redox")))]
+#[cfg(all(any(unix, target_os = "wasi"), not(target_os = "macos"), not(target_os = "ios"), not(target_os = "redox")))]
 use libc::clock_gettime;