diff --git a/ocat b/ocat
index 11a4c91f..6cbe071c 100755
Binary files a/ocat and b/ocat differ
diff --git a/showdef b/showdef
index f5fd9a84..b8912125 100755
Binary files a/showdef and b/showdef differ
diff --git a/src/lib/system/linux/clang/Console.Mod b/src/lib/system/linux/clang/Console.Mod
index e523ef7b..9b6b6611 100644
--- a/src/lib/system/linux/clang/Console.Mod
+++ b/src/lib/system/linux/clang/Console.Mod
@@ -7,6 +7,10 @@ MODULE Console;  (* J. Templ, 29-June-96 *)
   VAR line: ARRAY 128 OF CHAR;
     pos: INTEGER;
 
+  (* for read(), write() *)
+  PROCEDURE -includeUnistd()
+    "#include <unistd.h>";
+
   PROCEDURE -Write(adr, n: LONGINT)
     "write(1/*stdout*/, adr, n)";
 
diff --git a/src/lib/system/linux/clang/x86_64/Unix.Mod b/src/lib/system/linux/clang/x86_64/Unix.Mod
index 7dfde70d..2e3099ce 100644
--- a/src/lib/system/linux/clang/x86_64/Unix.Mod
+++ b/src/lib/system/linux/clang/x86_64/Unix.Mod
@@ -313,6 +313,14 @@ from man gettimeofday
   PROCEDURE -includeErrno()
     "#include <errno.h>";
 
+  (* for read(), write() *)
+  PROCEDURE -includeUnistd()
+    "#include <unistd.h>";
+
+  (* for system() *)
+  PROCEDURE -includeStdlib()
+    "#include <stdlib.h>";
+
   PROCEDURE -err(): LONGINT
     "errno";
 
diff --git a/voc b/voc
index 9986ddb2..675d9ee5 100755
Binary files a/voc and b/voc differ
diff --git a/vocstatic.linux.clang.x86_64 b/vocstatic.linux.clang.x86_64
index 9986ddb2..675d9ee5 100755
Binary files a/vocstatic.linux.clang.x86_64 and b/vocstatic.linux.clang.x86_64 differ