diff --git a/gopls/internal/regtest/modfile/modfile_test.go b/gopls/internal/regtest/modfile/modfile_test.go
index 6c94bfb464..8592a96dc9 100644
--- a/gopls/internal/regtest/modfile/modfile_test.go
+++ b/gopls/internal/regtest/modfile/modfile_test.go
@@ -6,6 +6,7 @@ package modfile
 
 import (
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -513,6 +514,10 @@ require (
 
 // Reproduces golang/go#38232.
 func TestUnknownRevision(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skipf("skipping test that fails for unknown reasons on plan9; see https://go.dev/issue/50477")
+	}
+
 	testenv.NeedsGo1Point(t, 14)
 
 	const unknown = `
diff --git a/internal/lsp/tests/tests.go b/internal/lsp/tests/tests.go
index 45d3ccd052..2589e77f41 100644
--- a/internal/lsp/tests/tests.go
+++ b/internal/lsp/tests/tests.go
@@ -16,6 +16,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -273,6 +274,9 @@ func RunTests(t *testing.T, dataDir string, includeMultiModule bool, f func(*tes
 			if mode == "MultiModule" {
 				// Some bug in 1.12 breaks reading markers, and it's not worth figuring out.
 				testenv.NeedsGo1Point(t, 13)
+				if runtime.GOOS == "plan9" {
+					t.Skipf("MultiModule setup fails for undiagnosed reasons on plan9; see https://go.dev/issue/50478")
+				}
 			}
 			datum := load(t, mode, dataDir)
 			t.Helper()