diff --git a/libowlps/owlps.h b/libowlps/owlps.h
index f5b3fa1..3d3d4f8 100644
--- a/libowlps/owlps.h
+++ b/libowlps/owlps.h
@@ -227,7 +227,7 @@ typedef struct _owl_autocalibration_order
 
 
 /* Global variables */
-owl_bool run ;
+extern owl_bool run ;
 
 
 /* Function error codes */