diff --git a/Transceiver52M/sigProcLib.h b/Transceiver52M/sigProcLib.h
index c20b1ec..3aaa62b 100644
--- a/Transceiver52M/sigProcLib.h
+++ b/Transceiver52M/sigProcLib.h
@@ -12,7 +12,8 @@
 
 */
 
-
+#ifndef SIGPROCLIB_H
+#define SIGPROCLIB_H
 
 #include "Vector.h"
 #include "Complex.h"
@@ -384,3 +385,5 @@
 		       int samplesPerSymbol,
 		       signalVector &w, 
 		       signalVector &b);
+
+#endif /* SIGPROCLIB_H */