diff --git a/include/system.h b/include/system.h
index a2cb51f..9f40fdd 100644
--- a/include/system.h
+++ b/include/system.h
@@ -60,17 +60,17 @@ typedef long off_t;
 #endif
 #ifndef SIG_RET_TYPE
 #if defined(NHSTDC) || defined(POSIX_TYPES) || defined(OS2) || defined(__DECC)
-#define SIG_RET_TYPE void (*)()
+#define SIG_RET_TYPE void (*)(int)
 #endif
 #endif
 #ifndef SIG_RET_TYPE
 #if defined(ULTRIX) || defined(SUNOS4) || defined(SVR3) || defined(SVR4)
 /* SVR3 is defined automatically by some systems */
-#define SIG_RET_TYPE void (*)()
+#define SIG_RET_TYPE void (*)(int)
 #endif
 #endif
 #ifndef SIG_RET_TYPE /* BSD, SIII, SVR2 and earlier, Sun3.5 and earlier */
-#define SIG_RET_TYPE int (*)()
+#define SIG_RET_TYPE int (*)(int)
 #endif
 
 #if !defined(__cplusplus) && !defined(__GO32__)
@@ -96,7 +96,7 @@ E long NDECL(lrand48);
 E void FDECL(srand48, (long));
 #else
 E long lrand48();
-E void srand48();
+E void srand48(long);
 #endif /* MACOSX */
 #endif /* BSD || ULTRIX || RANDOM */
 
@@ -352,10 +352,10 @@ E char *FDECL(memset, (char *, int, int));
 #endif /* MICRO */
 
 #if defined(BSD) && defined(ultrix) /* i.e., old versions of Ultrix */
-E void sleep();
+E void sleep(unsigned);
 #endif
 #if defined(ULTRIX) || defined(SYSV)
-E unsigned sleep();
+E unsigned sleep(unsigned);
 #endif
 #if defined(HPUX)
 E unsigned int FDECL(sleep, (unsigned int));
@@ -519,7 +519,7 @@ E char *FDECL(tgoto, (const char *, int, int));
 #else
 #if !(defined(HPUX) && defined(_POSIX_SOURCE))
 E int FDECL(tgetent, (char *, const char *));
-E void FDECL(tputs, (const char *, int, int (*)()));
+E void FDECL(tputs, (const char *, int, int (*)(int)));
 #endif
 E int FDECL(tgetnum, (const char *));
 E int FDECL(tgetflag, (const char *));
diff --git a/include/winX.h b/include/winX.h
index a1a5605..1d6b84b 100644
--- a/include/winX.h
+++ b/include/winX.h
@@ -279,7 +279,7 @@ typedef struct {
 } AppResources;
 
 E AppResources appResources;
-E void (*input_func)();
+E void (*input_func)(Widget, XEvent *, String *, Cardinal *);
 
 extern struct window_procs X11_procs;
 
diff --git a/include/xwindow.h b/include/xwindow.h
index 8b9cfa0..8307c25 100644
--- a/include/xwindow.h
+++ b/include/xwindow.h
@@ -76,8 +76,10 @@
 #define XtNexposeCallback "exposeCallback"
 #define XtNresizeCallback "resizeCallback"
 
-extern XFontStruct *WindowFontStruct(/* Widget */);
-extern Font WindowFont(/* Widget */);
+struct Widget;
+
+extern XFontStruct *WindowFontStruct(Widget);
+extern Font WindowFont(Widget);
 
 #define XtCWindowResource "WindowResource"
 #define XtCRows "Rows"