diff --git a/tests/compile-fail/concurrency/libc_pthread_create_main_terminate.rs b/tests/compile-fail/concurrency/libc_pthread_create_main_terminate.rs
index ea11691955c..35ee03242d1 100644
--- a/tests/compile-fail/concurrency/libc_pthread_create_main_terminate.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_create_main_terminate.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 // error-pattern: unsupported operation: the main thread terminated without waiting for other threads
 
 // Check that we terminate the program when the main thread terminates.
diff --git a/tests/compile-fail/concurrency/libc_pthread_join_detached.rs b/tests/compile-fail/concurrency/libc_pthread_join_detached.rs
index ad83fb2efef..dcd06596de1 100644
--- a/tests/compile-fail/concurrency/libc_pthread_join_detached.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_join_detached.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 
 // Joining a detached thread is undefined behavior.
 
diff --git a/tests/compile-fail/concurrency/libc_pthread_join_joined.rs b/tests/compile-fail/concurrency/libc_pthread_join_joined.rs
index 3ca04244969..26f33f1f5f9 100644
--- a/tests/compile-fail/concurrency/libc_pthread_join_joined.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_join_joined.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 
 // Joining an already joined thread is undefined behavior.
 
diff --git a/tests/compile-fail/concurrency/libc_pthread_join_main.rs b/tests/compile-fail/concurrency/libc_pthread_join_main.rs
index 69e1a68ef97..15e43776ab8 100644
--- a/tests/compile-fail/concurrency/libc_pthread_join_main.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_join_main.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 
 // Joining the main thread is undefined behavior.
 
diff --git a/tests/compile-fail/concurrency/libc_pthread_join_multiple.rs b/tests/compile-fail/concurrency/libc_pthread_join_multiple.rs
index f8a43cfcde6..d86233a6764 100644
--- a/tests/compile-fail/concurrency/libc_pthread_join_multiple.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_join_multiple.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 
 // Joining the same thread from multiple threads is undefined behavior.
 
diff --git a/tests/compile-fail/concurrency/libc_pthread_join_self.rs b/tests/compile-fail/concurrency/libc_pthread_join_self.rs
index d765a95d8be..2a8fe12eafd 100644
--- a/tests/compile-fail/concurrency/libc_pthread_join_self.rs
+++ b/tests/compile-fail/concurrency/libc_pthread_join_self.rs
@@ -1,4 +1,4 @@
-// ignore-windows: Concurrency on Windows is not supported yet.
+// ignore-windows: No libc on Windows
 
 // Joining itself is undefined behavior.
 
diff --git a/tests/compile-fail/environ-gets-deallocated.rs b/tests/compile-fail/environ-gets-deallocated.rs
index 0f374a2e3f8..b5a4441d2f9 100644
--- a/tests/compile-fail/environ-gets-deallocated.rs
+++ b/tests/compile-fail/environ-gets-deallocated.rs
@@ -1,4 +1,4 @@
-//ignore-windows: Windows does not have a global environ list that the program can access directly
+// ignore-windows: Windows does not have a global environ list that the program can access directly
 
 #[cfg(target_os="linux")]
 fn get_environ() -> *const *const u8 {
diff --git a/tests/run-pass/calloc.rs b/tests/run-pass/calloc.rs
index 4c520da85e8..6793f86c116 100644
--- a/tests/run-pass/calloc.rs
+++ b/tests/run-pass/calloc.rs
@@ -1,4 +1,4 @@
-//ignore-windows: Uses POSIX APIs
+// ignore-windows: No libc on Windows
 
 #![feature(rustc_private)]
 
diff --git a/tests/run-pass/malloc.rs b/tests/run-pass/malloc.rs
index f66263425ee..8e0d9ac6293 100644
--- a/tests/run-pass/malloc.rs
+++ b/tests/run-pass/malloc.rs
@@ -1,4 +1,4 @@
-//ignore-windows: Uses POSIX APIs
+// ignore-windows: No libc on Windows
 
 #![feature(rustc_private)]
 
diff --git a/tests/run-pass/thread-local.rs b/tests/run-pass/thread-local.rs
index 8de45811be4..1aa442edad3 100644
--- a/tests/run-pass/thread-local.rs
+++ b/tests/run-pass/thread-local.rs
@@ -1,4 +1,4 @@
-//ignore-windows: Uses POSIX APIs
+// ignore-windows: No libc on Windows
 
 #![feature(rustc_private)]
 extern crate libc;