diff --git a/Libraries/LibC/errno_numbers.h b/Libraries/LibC/errno_numbers.h
index c805cf2985..356803b581 100644
--- a/Libraries/LibC/errno_numbers.h
+++ b/Libraries/LibC/errno_numbers.h
@@ -98,4 +98,5 @@
 #define ENOTHREAD 70
 #define EPROTO 71
 #define ENOTSUP 72
-#define EMAXERRNO 73
+#define EPFNOSUPPORT 73
+#define EMAXERRNO 74
diff --git a/Libraries/LibC/string.cpp b/Libraries/LibC/string.cpp
index 744f6fc470..3a71088987 100644
--- a/Libraries/LibC/string.cpp
+++ b/Libraries/LibC/string.cpp
@@ -363,6 +363,7 @@ const char* const sys_errlist[] = {
     "No such thread",
     "Protocol error",
     "Not supported",
+    "Protocol family not supported",
     "The highest errno +1 :^)",
 };