diff --git a/lib/libc/stdio/ferror.c b/lib/libc/stdio/ferror.c
index 27ca10744d09..a245128ef0be 100644
--- a/lib/libc/stdio/ferror.c
+++ b/lib/libc/stdio/ferror.c
@@ -45,7 +45,7 @@ static char sccsid[] = "@(#)ferror.c	8.1 (Berkeley) 6/4/93";
  */
 #undef ferror
 
-ferror(fp)
+int ferror(fp)
 	FILE *fp;
 {
 	return (__sferror(fp));
diff --git a/lib/libc/stdio/fgetln.c b/lib/libc/stdio/fgetln.c
index ec81a2dafc06..ea99f4d8b650 100644
--- a/lib/libc/stdio/fgetln.c
+++ b/lib/libc/stdio/fgetln.c
@@ -50,7 +50,7 @@ static char sccsid[] = "@(#)fgetln.c	8.2 (Berkeley) 1/2/94";
  * so we add 1 here.
 #endif
  */
-__slbexpand(fp, newsize)
+int __slbexpand(fp, newsize)
 	FILE *fp;
 	size_t newsize;
 {
diff --git a/lib/libc/stdio/fileno.c b/lib/libc/stdio/fileno.c
index 91e82e8b1ebf..327beddb8d48 100644
--- a/lib/libc/stdio/fileno.c
+++ b/lib/libc/stdio/fileno.c
@@ -45,7 +45,7 @@ static char sccsid[] = "@(#)fileno.c	8.1 (Berkeley) 6/4/93";
  */
 #undef fileno
 
-fileno(fp)
+int fileno(fp)
 	FILE *fp;
 {
 	return (__sfileno(fp));
diff --git a/lib/libc/stdio/flags.c b/lib/libc/stdio/flags.c
index ee1a76cef728..6ec19e45ac6c 100644
--- a/lib/libc/stdio/flags.c
+++ b/lib/libc/stdio/flags.c
@@ -48,7 +48,7 @@ static char sccsid[] = "@(#)flags.c	8.1 (Berkeley) 6/4/93";
  * to be passed to an open() syscall through *optr.
  * Return 0 on error.
  */
-__sflags(mode, optr)
+int __sflags(mode, optr)
 	register char *mode;
 	int *optr;
 {
diff --git a/lib/libc/stdio/fprintf.c b/lib/libc/stdio/fprintf.c
index 479ee24e936f..c6ece4532de2 100644
--- a/lib/libc/stdio/fprintf.c
+++ b/lib/libc/stdio/fprintf.c
@@ -46,7 +46,7 @@ static char sccsid[] = "@(#)fprintf.c	8.1 (Berkeley) 6/4/93";
 #endif
 
 #if __STDC__
-fprintf(FILE *fp, const char *fmt, ...)
+int fprintf(FILE *fp, const char *fmt, ...)
 #else
 fprintf(fp, fmt, va_alist)
 	FILE *fp;