diff --git a/src/basic/namespace-util.c b/src/basic/namespace-util.c
index 74c3ca04218..a55b76df97b 100644
--- a/src/basic/namespace-util.c
+++ b/src/basic/namespace-util.c
@@ -10,6 +10,7 @@
 #include "namespace-util.h"
 #include "process-util.h"
 #include "stat-util.h"
+#include "stdio-util.h"
 #include "user-util.h"
 
 int namespace_open(pid_t pid, int *pidns_fd, int *mntns_fd, int *netns_fd, int *userns_fd, int *root_fd) {
@@ -82,15 +83,14 @@ int namespace_open(pid_t pid, int *pidns_fd, int *mntns_fd, int *netns_fd, int *
 }
 
 int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int root_fd) {
-        if (userns_fd >= 0) {
-                /* Can't setns to your own userns, since then you could
-                 * escalate from non-root to root in your own namespace, so
-                 * check if namespaces equal before attempting to enter. */
-                _cleanup_free_ char *userns_fd_path = NULL;
-                int r;
-                if (asprintf(&userns_fd_path, "/proc/self/fd/%d", userns_fd) < 0)
-                        return -ENOMEM;
+        int r;
 
+        if (userns_fd >= 0) {
+                /* Can't setns to your own userns, since then you could escalate from non-root to root in
+                 * your own namespace, so check if namespaces are equal before attempting to enter. */
+
+                char userns_fd_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+                xsprintf(userns_fd_path, "/proc/self/fd/%d", userns_fd);
                 r = files_same(userns_fd_path, "/proc/self/ns/user", 0);
                 if (r < 0)
                         return r;