diff --git a/unix/internal/mkmerge/mkmerge_test.go b/unix/internal/mkmerge/mkmerge_test.go
index 3207244..e61d7d4 100644
--- a/unix/internal/mkmerge/mkmerge_test.go
+++ b/unix/internal/mkmerge/mkmerge_test.go
@@ -410,6 +410,10 @@
 		}
 
 		got, err := filter(inFiles[0].src, commonSet.keepCommon)
+		if err != nil {
+			t.Fatal(err)
+		}
+
 		expected := []byte(mergedFile)
 
 		if !bytes.Equal(got, expected) {
diff --git a/unix/syscall_freebsd_test.go b/unix/syscall_freebsd_test.go
index 0841148..de02a1a 100644
--- a/unix/syscall_freebsd_test.go
+++ b/unix/syscall_freebsd_test.go
@@ -221,14 +221,14 @@
 		panic(fmt.Sprintf("CapRightsIsSet failed: %s %#v", err, err))
 	}
 	if !b {
-		panic(fmt.Sprintf("Unexpected rights"))
+		panic("Unexpected rights")
 	}
 	b, err = unix.CapRightsIsSet(r, []uint64{unix.CAP_READ, unix.CAP_LOOKUP, unix.CAP_WRITE})
 	if err != nil {
 		panic(fmt.Sprintf("CapRightsIsSet failed: %s %#v", err, err))
 	}
 	if b {
-		panic(fmt.Sprintf("Unexpected rights (2)"))
+		panic("Unexpected rights (2)")
 	}
 
 	// Can no longer create a file