diff --git a/internal/rosa/gnu.go b/internal/rosa/gnu.go
index ed127b0..71f4b7d 100644
--- a/internal/rosa/gnu.go
+++ b/internal/rosa/gnu.go
@@ -1,11 +1,6 @@
 package rosa
 
-import (
-	"runtime"
-	"strconv"
-
-	"hakurei.app/internal/pkg"
-)
+import "hakurei.app/internal/pkg"
 
 func (t Toolchain) newM4() pkg.Artifact {
 	const (
@@ -53,9 +48,10 @@ func (t Toolchain) newAutoconf() pkg.Artifact {
 		mustDecode(checksum),
 		pkg.TarGzip,
 	), &MakeAttr{
-		Env: []string{
-			"TESTSUITEFLAGS=" + strconv.Itoa(runtime.NumCPU()),
+		Make: []string{
+			`TESTSUITEFLAGS="-j$(nproc)"`,
 		},
+		Flag: TExclusive,
 	},
 		t.Load(M4),
 		t.Load(Perl),
@@ -109,8 +105,8 @@ func (t Toolchain) newLibtool() pkg.Artifact {
 		mustDecode(checksum),
 		pkg.TarGzip,
 	), &MakeAttr{
-		Env: []string{
-			"TESTSUITEFLAGS=" + strconv.Itoa(runtime.NumCPU()),
+		Make: []string{
+			`TESTSUITEFLAGS=32`,
 		},
 	},
 		t.Load(M4),