diff --git a/libc-test/semver/illumos.txt b/libc-test/semver/illumos.txt
index 64c25d4b4f96..df91859b4665 100644
--- a/libc-test/semver/illumos.txt
+++ b/libc-test/semver/illumos.txt
@@ -12,3 +12,4 @@ pthread_attr_get_np
 pthread_attr_getstackaddr
 pthread_attr_setstack
 ptsname_r
+syncfs
diff --git a/src/unix/solarish/illumos.rs b/src/unix/solarish/illumos.rs
index 614fd12eb07e..9b0a692055e6 100644
--- a/src/unix/solarish/illumos.rs
+++ b/src/unix/solarish/illumos.rs
@@ -112,4 +112,6 @@ extern "C" {
     pub fn getpagesizes2(pagesize: *mut ::size_t, nelem: ::c_int) -> ::c_int;
 
     pub fn ptsname_r(fildes: ::c_int, name: *mut ::c_char, namelen: ::size_t) -> ::c_int;
+
+    pub fn syncfs(fd: ::c_int) -> ::c_int;
 }