diff --git a/lib/libc/stdlib/getenv.3 b/lib/libc/stdlib/getenv.3
index 3d365f16a26b..35547aa6b332 100644
--- a/lib/libc/stdlib/getenv.3
+++ b/lib/libc/stdlib/getenv.3
@@ -50,21 +50,17 @@
 .Ft int
 .Fn setenv "const char *name" "const char *value" "int overwrite"
 .Ft int
-.Fn putenv "const char *string"
-.Ft void
+.Fn putenv "char *string"
+.Ft int
 .Fn unsetenv "const char *name"
 .Sh DESCRIPTION
 These functions set, unset and fetch environment variables from the
 host
 .Em environment list .
 For compatibility with differing environment conventions,
-the given arguments
-.Fa name
-and
+the given argument
 .Fa value
-may be appended and prepended,
-respectively,
-with an equal sign
+may be prepended with an equal sign
 .Dq Li \&= .
 .Pp
 The
@@ -121,9 +117,21 @@ is not in the current environment,
 .Dv NULL
 is returned.
 .Pp
-.Rv -std setenv putenv
+.Rv -std setenv putenv unsetenv
 .Sh ERRORS
 .Bl -tag -width Er
+.It Bq Er EINVAL
+The function
+.Fn setenv
+or
+.Fn unsetenv
+failed because the
+.Fa name
+is a
+.Dv NULL
+pointer, points to an empty string, or points to a string containing an
+.Dq Li \&=
+character.
 .It Bq Er ENOMEM
 The function
 .Fn setenv
@@ -141,6 +149,12 @@ The
 .Fn getenv
 function conforms to
 .St -isoC .
+The
+.Fn setenv
+and
+.Fn unsetenv
+functions conforms to
+.St -p1003.1-2001 .
 .Sh HISTORY
 The functions
 .Fn setenv
diff --git a/lib/libc/stdlib/getenv.c b/lib/libc/stdlib/getenv.c
index 306b6a19f8be..73ac407b4314 100644
--- a/lib/libc/stdlib/getenv.c
+++ b/lib/libc/stdlib/getenv.c
@@ -44,7 +44,6 @@ inline char *__findenv(const char *, int *);
  *	Returns pointer to value associated with name, if any, else NULL.
  *	Sets offset to be the offset of the name/value combination in the
  *	environmental array, for use by setenv(3) and unsetenv(3).
- *	Explicitly removes '=' in argument name.
  *
  *	This routine *should* be a static; don't use it.
  */
@@ -58,11 +57,9 @@ __findenv(name, offset)
 	const char *np;
 	char **p, *cp;
 
-	if (name == NULL || environ == NULL)
+	if (environ == NULL)
 		return (NULL);
-	for (np = name; *np && *np != '='; ++np)
-		continue;
-	len = np - name;
+	len = strlen(name);
 	for (p = environ; (cp = *p) != NULL; ++p) {
 		for (np = name, i = len; i && *cp; i--)
 			if (*cp++ != *np++)
@@ -85,5 +82,8 @@ getenv(name)
 {
 	int offset;
 
+	if (name == NULL || !*name || strchr(name, '=') != NULL)
+		return (NULL);
+
 	return (__findenv(name, &offset));
 }
diff --git a/lib/libc/stdlib/putenv.c b/lib/libc/stdlib/putenv.c
index a5eea5d0ddfd..b6c7ccb67f83 100644
--- a/lib/libc/stdlib/putenv.c
+++ b/lib/libc/stdlib/putenv.c
@@ -33,24 +33,28 @@ static char sccsid[] = "@(#)putenv.c	8.2 (Berkeley) 3/27/94";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
 int
 putenv(str)
-	const char *str;
+	char *str;
 {
 	char *p, *equal;
-	int rval;
+	int rval, serrno;
 
 	if ((p = strdup(str)) == NULL)
 		return (-1);
 	if ((equal = index(p, '=')) == NULL) {
 		(void)free(p);
+		errno = EINVAL;
 		return (-1);
 	}
 	*equal = '\0';
 	rval = setenv(p, equal + 1, 1);
+	serrno = errno;
 	(void)free(p);
+	errno = serrno;
 	return (rval);
 }
diff --git a/lib/libc/stdlib/setenv.c b/lib/libc/stdlib/setenv.c
index 202c022ebfcf..4f05f3207baf 100644
--- a/lib/libc/stdlib/setenv.c
+++ b/lib/libc/stdlib/setenv.c
@@ -33,6 +33,7 @@ static char sccsid[] = "@(#)setenv.c	8.1 (Berkeley) 6/4/93";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <errno.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
@@ -55,6 +56,11 @@ setenv(name, value, rewrite)
 	char *c;
 	int l_value, offset;
 
+	if (name == NULL || !*name || strchr(name, '=') != NULL) {
+		errno = EINVAL;
+		return (-1);
+	}
+
 	if (*value == '=')			/* no `=' in value */
 		++value;
 	l_value = strlen(value);
@@ -88,9 +94,8 @@ setenv(name, value, rewrite)
 		environ[cnt + 1] = NULL;
 		offset = cnt;
 	}
-	for (c = (char *)name; *c && *c != '='; ++c);	/* no `=' in name */
 	if (!(environ[offset] =			/* name + `=' + value */
-	    malloc((size_t)((int)(c - name) + l_value + 2))))
+	    malloc((size_t)(strlen(name) + l_value + 2))))
 		return (-1);
 	for (c = environ[offset]; (*c = *name++) && *c != '='; ++c);
 	for (*c++ = '='; (*c++ = *value++); );
@@ -101,7 +106,7 @@ setenv(name, value, rewrite)
  * unsetenv(name) --
  *	Delete environmental variable "name".
  */
-void
+int
 unsetenv(name)
 	const char *name;
 {
@@ -109,8 +114,14 @@ unsetenv(name)
 	char **p;
 	int offset;
 
+	if (name == NULL || !*name || strchr(name, '=') != NULL) {
+		errno = EINVAL;
+		return (-1);
+	}
+
 	while (__findenv(name, &offset))	/* if set multiple times */
 		for (p = &environ[offset];; ++p)
 			if (!(*p = *(p + 1)))
 				break;
+	return (0);
 }