diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm
index eb5dbf94a31000e2ec198c51ae8b9becd1f306f8..ec68679f0b61fa8fea1d073b12f24584127a4222 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -41,7 +41,7 @@ (define (unprivileged-user-namespace-supported?)
   "Return #t if user namespaces can be created by unprivileged users."
   (let ((userns-file "/proc/sys/kernel/unprivileged_userns_clone"))
     (if (file-exists? userns-file)
-        (string=? "1" (call-with-input-file userns-file read-string))
+        (eqv? #\1 (call-with-input-file userns-file read-char))
         #t)))
 
 (define (setgroups-supported?)