diff --git a/lib/libgpib/ibfoo.c b/lib/libgpib/ibfoo.c
index a1905c6202b4..19c61ef76661 100644
--- a/lib/libgpib/ibfoo.c
+++ b/lib/libgpib/ibfoo.c
@@ -581,51 +581,51 @@ ibwait (int handle, int mask)
 }
 
 int
-ibwrt (int handle, void * buffer, long cnt)
+ibwrt (int handle, const void *buffer, long cnt)
 {
 	struct ibfoo_iocarg io;
 
 	io.__ident = __ID_IBWRT;
 	io.handle = handle;
-	io.buffer = buffer;
+	io.buffer = __DECONST(void *, buffer);
 	io.cnt = cnt;
 	io.__field = __F_HANDLE | __F_BUFFER | __F_CNT;
 	return (__ibsubmit(&io));
 }
 
 int
-ibwrta (int handle, void * buffer, long cnt)
+ibwrta (int handle, const void * buffer, long cnt)
 {
 	struct ibfoo_iocarg io;
 
 	io.__ident = __ID_IBWRTA;
 	io.handle = handle;
-	io.buffer = buffer;
+	io.buffer = __DECONST(void *, buffer);
 	io.cnt = cnt;
 	io.__field = __F_HANDLE | __F_BUFFER | __F_CNT;
 	return (__ibsubmit(&io));
 }
 
 int
-ibwrtf (int handle, char * flname)
+ibwrtf (int handle, const char *flname)
 {
 	struct ibfoo_iocarg io;
 
 	io.__ident = __ID_IBWRTF;
 	io.handle = handle;
-	io.flname = flname;
+	io.flname = __DECONST(void *, flname);
 	io.__field = __F_HANDLE | __F_FLNAME;
 	return (__ibsubmit(&io));
 }
 
 int
-ibwrtkey (int handle, void * buffer, int cnt)
+ibwrtkey (int handle, const void *buffer, int cnt)
 {
 	struct ibfoo_iocarg io;
 
 	io.__ident = __ID_IBWRTKEY;
 	io.handle = handle;
-	io.buffer = buffer;
+	io.buffer = __DECONST(void *, buffer);
 	io.cnt = cnt;
 	io.__field = __F_HANDLE | __F_BUFFER | __F_CNT;
 	return (__ibsubmit(&io));
diff --git a/sys/dev/ieee488/ugpib.h b/sys/dev/ieee488/ugpib.h
index 77b7fcd19334..04467c745c8a 100644
--- a/sys/dev/ieee488/ugpib.h
+++ b/sys/dev/ieee488/ugpib.h
@@ -143,10 +143,10 @@ int ibtmo(int handle, int tmo);
 int ibtrap(int  mask, int mode);
 int ibtrg(int handle);
 int ibwait(int handle, int mask);
-int ibwrt(int handle, void *buffer, long cnt);
-int ibwrta(int handle, void *buffer, long cnt);
-int ibwrtf(int handle, char *flname);
-int ibwrtkey(int handle, void *buffer, int cnt);
+int ibwrt(int handle, const void *buffer, long cnt);
+int ibwrta(int handle, const void *buffer, long cnt);
+int ibwrtf(int handle, const char *flname);
+int ibwrtkey(int handle, const void *buffer, int cnt);
 int ibxtrc(int handle, void *buffer, long cnt);
 #endif /* _KERNEL */
 #endif /* _DEV_IEEE488_UGPIB_H_ */