diff --git a/mantle/cmd/kola/testiso.go b/mantle/cmd/kola/testiso.go
index 206494a2c7..be9b3d0ecc 100644
--- a/mantle/cmd/kola/testiso.go
+++ b/mantle/cmd/kola/testiso.go
@@ -99,9 +99,6 @@ var (
 		// "iso-offline-install.4k.s390fw",
 		"pxe-online-install.s390fw",
 		"pxe-offline-install.s390fw",
-		"miniso-install.s390fw",
-		"miniso-install.nm.s390fw",
-		"miniso-install.4k.nm.s390fw",
 	}
 	tests_ppc64le = []string{
 		"iso-live-login.ppcfw",
diff --git a/mantle/platform/qemu.go b/mantle/platform/qemu.go
index ab40a2623f..1268f1f3ed 100644
--- a/mantle/platform/qemu.go
+++ b/mantle/platform/qemu.go
@@ -1396,6 +1396,13 @@ func coreosInstallerSupportsISOKargs() (bool, error) {
 	return strings.Contains(out, "kargs"), nil
 }
 
+// supportsIsoKargs returns true if we support modifying ISO kargs on the
+// current arch. We could also auto-detect this, but would probably still want
+// some assertions that we detected as supported on !s390x.
+func (builder *QemuBuilder) supportsIsoKargs() bool {
+	return builder.architecture != "s390x"
+}
+
 func (builder *QemuBuilder) setupIso() error {
 	if err := builder.ensureTempdir(); err != nil {
 		return err
@@ -1440,9 +1447,11 @@ func (builder *QemuBuilder) setupIso() error {
 				return errors.Wrapf(err, "running `coreos-installer iso kargs modify`; old CoreOS ISO?")
 			}
 			// Only actually emit a warning if we expected it to be supported
-			stderr := stderrb.String()
-			plog.Warningf("running coreos-installer iso kargs modify: %v: %q", err, stderr)
-			plog.Warning("likely targeting an old CoreOS ISO; ignoring...")
+			if builder.supportsIsoKargs() {
+				stderr := stderrb.String()
+				plog.Warningf("running coreos-installer iso kargs modify: %v: %q", err, stderr)
+				plog.Warning("likely targeting an old CoreOS ISO; ignoring...")
+			}
 		}
 	} else if len(builder.AppendKernelArgs) > 0 {
 		return fmt.Errorf("coreos-installer does not support appending kernel args")