diff --git a/lib/pwdutils.c b/lib/pwdutils.c
index 641a9da40..1c1f13e92 100644
--- a/lib/pwdutils.c
+++ b/lib/pwdutils.c
@@ -3,6 +3,7 @@
  * it what you wish.
  */
 #include <stdlib.h>
+#include <assert.h>
 
 #include "c.h"
 #include "pwdutils.h"
@@ -17,8 +18,8 @@ struct passwd *xgetpwnam(const char *username, char **pwdbuf)
 	struct passwd *pwd = NULL, *res = NULL;
 	int rc;
 
-	if (!pwdbuf || !username)
-		return NULL;
+	assert(pwdbuf);
+	assert(username);
 
 	*pwdbuf = xmalloc(UL_GETPW_BUFSIZ);
 	pwd = xcalloc(1, sizeof(struct passwd));
@@ -49,8 +50,8 @@ struct group *xgetgrnam(const char *groupname, char **grpbuf)
 	struct group *grp = NULL, *res = NULL;
 	int rc;
 
-	if (!grpbuf || !groupname)
-		return NULL;
+	assert(grpbuf);
+	assert(groupname);
 
 	*grpbuf = xmalloc(UL_GETPW_BUFSIZ);
 	grp = xcalloc(1, sizeof(struct group));
@@ -77,8 +78,7 @@ struct passwd *xgetpwuid(uid_t uid, char **pwdbuf)
 	struct passwd *pwd = NULL, *res = NULL;
 	int rc;
 
-	if (!pwdbuf)
-		return NULL;
+	assert(pwdbuf);
 
 	*pwdbuf = xmalloc(UL_GETPW_BUFSIZ);
 	pwd = xcalloc(1, sizeof(struct passwd));