diff --git a/PyMca/specfile/src/sfwrite.c b/PyMca/specfile/src/sfwrite.c
index 24df907..93c18e9 100755
--- a/PyMca/specfile/src/sfwrite.c
+++ b/PyMca/specfile/src/sfwrite.c
@@ -55,6 +55,7 @@
  */
 #include <SpecFile.h>
 #include <SpecFileP.h>
+#include <unistd.h>
 
 /*
  * Declarations