diff --git a/build/pkgs/arb/distros/homebrew.txt b/build/pkgs/arb/distros/homebrew.txt
index 9a7a5bca0a1..86c41dbaa5f 100644
--- a/build/pkgs/arb/distros/homebrew.txt
+++ b/build/pkgs/arb/distros/homebrew.txt
@@ -1,3 +1 @@
-## This package depends on ntl, the homebrew package of which we cannot use
-## because it is built with NTL_THREADS.  See https://trac.sagemath.org/ticket/29339
-# sagemath/science/arb
+arb
diff --git a/build/pkgs/flint/distros/homebrew.txt b/build/pkgs/flint/distros/homebrew.txt
index 9d130adb880..61c2ffe155a 100644
--- a/build/pkgs/flint/distros/homebrew.txt
+++ b/build/pkgs/flint/distros/homebrew.txt
@@ -1,3 +1 @@
-## This package depends on ntl, the homebrew package of which we cannot use
-## because it is built with NTL_THREADS.  See https://trac.sagemath.org/ticket/29339
-# sagemath/science/flint
+flint
diff --git a/build/pkgs/ntl/distros/homebrew.txt b/build/pkgs/ntl/distros/homebrew.txt
index 6664b6c5bd4..9f4d4f8fdb6 100644
--- a/build/pkgs/ntl/distros/homebrew.txt
+++ b/build/pkgs/ntl/distros/homebrew.txt
@@ -1,3 +1 @@
-## We cannot use ntl on homebrew because it is built with NTL_THREADS.
-## See https://trac.sagemath.org/ticket/29339
-# ntl
+ntl
diff --git a/src/sage/rings/polynomial/plural.pyx b/src/sage/rings/polynomial/plural.pyx
index c2792aec880..08b2ed72111 100644
--- a/src/sage/rings/polynomial/plural.pyx
+++ b/src/sage/rings/polynomial/plural.pyx
@@ -367,6 +367,8 @@ cdef class NCPolynomialRing_plural(Ring):
             True
             sage: H is loads(dumps(H))  # indirect doctest
             True
+            sage: A2.<x,y,z> = FreeAlgebra(GF(5), 3)
+            sage: R2 = A2.g_algebra({y*x:x*y-z, z*x:x*z+2*x, z*y:y*z-2*y}, order=TermOrder('degrevlex', 2))
 
         Check that :trac:`17224` is fixed::