diff --git a/lib/libpam/openpam_findenv.c b/lib/libpam/openpam_findenv.c
index 1e2854c..23e3196 100644
--- a/lib/libpam/openpam_findenv.c
+++ b/lib/libpam/openpam_findenv.c
@@ -39,6 +39,7 @@
 # include "config.h"
 #endif
 
+#include <errno.h>
 #include <string.h>
 
 #include <security/pam_appl.h>
@@ -63,6 +64,7 @@ openpam_findenv(pam_handle_t *pamh,
 		if (strncmp(pamh->env[i], name, len) == 0 &&
 		    pamh->env[i][len] == '=')
 			RETURNN(i);
+	errno = ENOENT;
 	RETURNN(-1);
 }
 
diff --git a/lib/libpam/pam_getenv.c b/lib/libpam/pam_getenv.c
index 94f9de7..86dc25e 100644
--- a/lib/libpam/pam_getenv.c
+++ b/lib/libpam/pam_getenv.c
@@ -39,6 +39,7 @@
 # include "config.h"
 #endif
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -61,8 +62,10 @@ pam_getenv(pam_handle_t *pamh,
 	int i;
 
 	ENTERS(name);
-	if (strchr(name, '=') != NULL)
+	if (strchr(name, '=') != NULL) {
+		errno = EINVAL;
 		RETURNS(NULL);
+	}
 	if ((i = openpam_findenv(pamh, name, strlen(name))) < 0)
 		RETURNS(NULL);
 	if ((str = strchr(pamh->env[i], '=')) == NULL)
diff --git a/lib/libpam/pam_putenv.c b/lib/libpam/pam_putenv.c
index 4e61db5..d7ac410 100644
--- a/lib/libpam/pam_putenv.c
+++ b/lib/libpam/pam_putenv.c
@@ -39,6 +39,7 @@
 # include "config.h"
 #endif
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -64,8 +65,10 @@ pam_putenv(pam_handle_t *pamh,
 	ENTER();
 
 	/* sanity checks */
-	if ((p = strchr(namevalue, '=')) == NULL)
+	if ((p = strchr(namevalue, '=')) == NULL) {
+		errno = EINVAL;
 		RETURNC(PAM_SYSTEM_ERR);
+	}
 
 	/* see if the variable is already in the environment */
 	if ((i = openpam_findenv(pamh, namevalue, p - namevalue)) >= 0) {
diff --git a/lib/libpam/pam_setenv.c b/lib/libpam/pam_setenv.c
index 0ee7724..6cf68c7 100644
--- a/lib/libpam/pam_setenv.c
+++ b/lib/libpam/pam_setenv.c
@@ -39,6 +39,7 @@
 # include "config.h"
 #endif
 
+#include <errno.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -67,8 +68,10 @@ pam_setenv(pam_handle_t *pamh,
 	ENTER();
 
 	/* sanity checks */
-	if (*name == '\0' || strchr(name, '=') != NULL)
+	if (*name == '\0' || strchr(name, '=') != NULL) {
+		errno = EINVAL;
 		RETURNC(PAM_SYSTEM_ERR);
+	}
 
 	/* is it already there? */
 	if (!overwrite && openpam_findenv(pamh, name, strlen(name)) >= 0)