diff --git a/gnu/packages/guile-xyz.scm b/gnu/packages/guile-xyz.scm
index 42b853f060..ca0999b622 100644
--- a/gnu/packages/guile-xyz.scm
+++ b/gnu/packages/guile-xyz.scm
@@ -620,7 +620,19 @@ (define-public guile-fibers-1.1
     (build-system gnu-build-system)
     (arguments
      (list #:make-flags
-           #~(list "GUILE_AUTO_COMPILE=0")))
+           #~(list "GUILE_AUTO_COMPILE=0")
+           #:phases
+           (if (target-x86-64?)
+             #~%standard-phases
+             #~(modify-phases %standard-phases
+                 (add-before 'check 'disable-some-tests
+                   (lambda _
+                     ;; This test can take more than an hour on some systems.
+                     (substitute* "tests/basic.scm"
+                       ((".*spawn-fiber loop-to-1e4.*") ""))
+                     ;; These tests can take more than an hour and/or segfault.
+                     (substitute* "Makefile"
+                       (("tests/speedup.scm") ""))))))))
     (native-inputs
      (list texinfo pkg-config autoconf automake libtool
            guile-3.0            ;for 'guild compile