diff --git a/Makefile.build b/Makefile.build
index d136a6f1c1e8fbc60df45bc898ef0d96fd7f53ed..39f59e1799b51fb8c9e84037d0c9203f468734e2 100644
--- a/Makefile.build
+++ b/Makefile.build
@@ -72,6 +72,7 @@ userprog_SRC += userprog/syscall_remove.c
 userprog_SRC += userprog/syscall_write.c
 userprog_SRC += userprog/file_descriptors_map.c
 userprog_SRC += userprog/syscall_read.c
+userprog_SRC += userprog/syscall_filesize.c
 
 # No virtual memory code yet.
 #vm_SRC = vm/file.c			# Some file.
diff --git a/userprog/syscall_filesize.c b/userprog/syscall_filesize.c
index ae8e45a80bf0e1ed618a6d54c5c416deacae49dd..aff7fe7a80c3666fd4d69ac8d7a35aaab5eb06aa 100644
--- a/userprog/syscall_filesize.c
+++ b/userprog/syscall_filesize.c
@@ -3,7 +3,7 @@
  *
  * Authored by Alex Stratford
  */
-
+#include <stddef.h>
 #include "system_calls.h"
 #include "filesys/file.h"
 
@@ -17,4 +17,4 @@ void syscall_filesize(struct intr_frame *f) {
 	// Using the file_length function in file.h to get the length and store it
 	int size = file_length(file); 
 	f->eax = size;
-}
\ No newline at end of file
+}