diff --git a/bin/sh/arith_yacc.c b/bin/sh/arith_yacc.c
index 48c63eac789c..fbf9a640c03b 100644
--- a/bin/sh/arith_yacc.c
+++ b/bin/sh/arith_yacc.c
@@ -84,6 +84,8 @@ static const char prec[ARITH_BINOP_MAX - ARITH_BINOP_MIN] = {
 
 #define ARITH_MAX_PREC 8
 
+int letcmd(int, char **);
+
 static __dead2 void yyerror(const char *s)
 {
 	error("arithmetic expression: %s: \"%s\"", s, arith_startbuf);
@@ -377,4 +379,3 @@ letcmd(int argc, char **argv)
 	out1fmt(ARITH_FORMAT_STR "\n", i);
 	return !i;
 }
-
diff --git a/bin/sh/arith_yylex.c b/bin/sh/arith_yylex.c
index cfb9724d524b..f6eebdba2640 100644
--- a/bin/sh/arith_yylex.c
+++ b/bin/sh/arith_yylex.c
@@ -53,7 +53,7 @@ __FBSDID("$FreeBSD$");
 extern const char *arith_buf;
 
 int
-yylex()
+yylex(void)
 {
 	int value;
 	const char *buf = arith_buf;
diff --git a/bin/sh/exec.c b/bin/sh/exec.c
index 468f940de201..82cb3ac9e1a3 100644
--- a/bin/sh/exec.c
+++ b/bin/sh/exec.c
@@ -493,7 +493,7 @@ hashcd(void)
  */
 
 void
-changepath(const char *newval)
+changepath(const char *newval __unused)
 {
 	clearcmdentry();
 }
diff --git a/bin/sh/histedit.c b/bin/sh/histedit.c
index e29bcab8ff1e..6371599e3b23 100644
--- a/bin/sh/histedit.c
+++ b/bin/sh/histedit.c
@@ -160,8 +160,7 @@ histedit(void)
 
 
 void
-sethistsize(hs)
-	const char *hs;
+sethistsize(const char *hs)
 {
 	int histsize;
 	HistEvent he;
diff --git a/bin/sh/jobs.c b/bin/sh/jobs.c
index 75b503ecaa79..232be8bf959f 100644
--- a/bin/sh/jobs.c
+++ b/bin/sh/jobs.c
@@ -92,6 +92,7 @@ static void restartjob(struct job *);
 #endif
 static void freejob(struct job *);
 static struct job *getjob(char *);
+pid_t getjobpgrp(char *);
 static pid_t dowait(int, struct job *);
 static pid_t waitproc(int, int *);
 static void checkzombies(void);