diff --git a/vm/os-unix.h b/vm/os-unix.h
index b8047855d6..6d220de903 100755
--- a/vm/os-unix.h
+++ b/vm/os-unix.h
@@ -6,6 +6,7 @@
 #include <sys/time.h>
 #include <dlfcn.h>
 #include <signal.h>
+#include <pthread.h>
 
 typedef char F_CHAR;
 typedef char F_SYMBOL;
diff --git a/vm/types.c b/vm/types.c
index 5b16a9afdb..3941f13042 100755
--- a/vm/types.c
+++ b/vm/types.c
@@ -12,7 +12,7 @@ bool to_boolean(CELL value)
 	return value != F;
 }
 
-CELL clone(CELL object)
+CELL clone_object(CELL object)
 {
 	CELL size = object_size(object);
 	if(size == 0)
@@ -31,7 +31,7 @@ CELL clone(CELL object)
 
 DEFINE_PRIMITIVE(clone)
 {
-	drepl(clone(dpeek()));
+	drepl(clone_object(dpeek()));
 }
 
 F_WORD *allot_word(CELL vocab, CELL name)