diff --git a/ruby.spec b/ruby.spec
index 0dab721..39123c4 100644
--- a/ruby.spec
+++ b/ruby.spec
@@ -533,10 +533,20 @@ DISABLE_TESTS=""
 DISABLE_TESTS="-x test_dl2.rb $DISABLE_TESTS"
 %endif
 
-%ifnarch ppc ppc64
-make check TESTS="-v $DISABLE_TESTS"
+%ifarch ppc ppc64
+# test_ioctl_linux(TestIO) fails with #<Errno::EINVAL: Invalid argument - /dev/urandom>.
+# https://bugs.ruby-lang.org/issues/7718
+DISABLE_TESTS="-x test_io.rb $DISABLE_TESTS"
+%endif
+
+%ifarch ppc
+# test_stack_size(TestFiber) fails.
+# https://bugs.ruby-lang.org/issues/7719
+DISABLE_TESTS="-x test_fiber.rb $DISABLE_TESTS"
 %endif
 
+make check TESTS="-v $DISABLE_TESTS"
+
 %post libs -p /sbin/ldconfig
 
 %postun libs -p /sbin/ldconfig