--- a/fidlib.h
+++ b/fidlib.h
@@ -2,6 +2,13 @@
 //	fidlib include file
 //
 
+#ifndef __FIDLIB_H
+#define __FIDLIB_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 typedef struct FidFilter FidFilter;
 struct FidFilter {
    short typ;		// Type of filter element 'I' IIR, 'F' FIR, or 0 for end of list
@@ -66,3 +73,9 @@
 extern void fid_run_zapbuf(void *buf);
 extern void fid_run_freebuf(void *runbuf);
 extern void fid_run_free(void *run);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __FIDLIB_H */