diff --git a/bin/sh/output.c b/bin/sh/output.c
index 88ef764991ff..bc8f1dfe4c08 100644
--- a/bin/sh/output.c
+++ b/bin/sh/output.c
@@ -115,7 +115,7 @@ open_mem(block, length, file)
 
 void
 out1str(p)
-	char *p;
+	const char *p;
 	{
 	outstr(p, out1);
 }
@@ -123,7 +123,7 @@ out1str(p)
 
 void
 out2str(p)
-	char *p;
+	const char *p;
 	{
 	outstr(p, out2);
 }
@@ -131,7 +131,7 @@ out2str(p)
 
 void
 outstr(p, file)
-	register char *p;
+	const register char *p;
 	register struct output *file;
 	{
 	while (*p)
diff --git a/bin/sh/output.h b/bin/sh/output.h
index 5b4764cdbf31..80e45f89d837 100644
--- a/bin/sh/output.h
+++ b/bin/sh/output.h
@@ -55,9 +55,9 @@ extern struct output *out2;
 
 
 #ifdef __STDC__
-void outstr(char *, struct output *);
-void out1str(char *);
-void out2str(char *);
+void outstr(const char *, struct output *);
+void out1str(const char *);
+void out2str(const char *);
 void outfmt(struct output *, char *, ...);
 void out1fmt(char *, ...);
 void fmtstr(char *, int, char *, ...);