diff --git a/libstdc++-v3/include/bits/std_mutex.h b/libstdc++-v3/include/bits/std_mutex.h
index bc515358d23..f74ddc4123a 100644
--- a/libstdc++-v3/include/bits/std_mutex.h
+++ b/libstdc++-v3/include/bits/std_mutex.h
@@ -36,6 +36,7 @@
 # include <bits/c++0x_warning.h>
 #else
 
+#include <errno.h> // EBUSY
 #include <bits/functexcept.h>
 #include <bits/gthr.h>