diff --git a/libc/include/errno.h b/libc/include/errno.h
index 4b61dc1a..003084cb 100644
--- a/libc/include/errno.h
+++ b/libc/include/errno.h
@@ -14,6 +14,7 @@
 #define ENOTEMPTY 10
 #define ENAMETOOLONG 11
 #define ENOBUFS 12
+#define ENOTTY 13
 
 __BEGIN_DECLS
 
diff --git a/libc/string.cpp b/libc/string.cpp
index 08dc4844..e23ba6d0 100644
--- a/libc/string.cpp
+++ b/libc/string.cpp
@@ -113,6 +113,9 @@ char* strerror(int error)
 	case ENOBUFS:
 		strcpy(buffer, "No buffer space available");
 		break;
+	case ENOTTY:
+		strcpy(buffer, "Inappropriate I/O control operation");
+		break;
 	default:
 		{
 			// FIXME: sprintf