diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index fd41b97..bd45581 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -11,11 +11,14 @@ on:
 # as it runs many builds under the hood.
 # The default -timeout=10m can be hit by the hosted runners.
 #
-# Also note that we don't use actions/cache for Go on purpose.
+# Also note that we don't use Actions caching for Go on purpose.
 # Caching GOMODCACHE wouldn't help much, as we have few deps.
 # Caching GOCACHE would do more harm than good,
 # as the tests redo most of their work if the garble version changes,
 # and the majority of commits or PRs will do so.
+# Moreover, GitHub saves and restores caches via compressed archives over the
+# network, which means it can easily add one minute of overhead on its own for
+# just a few hundred megabytes worth of files.
 
 name: Test
 jobs:
@@ -27,10 +30,11 @@ jobs:
         os: [ubuntu-latest, macos-11, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/setup-go@v3
+    - uses: actions/checkout@v3
+    - uses: actions/setup-go@v4
       with:
         go-version: ${{ matrix.go-version }}
-    - uses: actions/checkout@v3
+        cache: false
     - name: Test
       run: go test -timeout=15m ./...
     - uses: actions/upload-artifact@v3
@@ -60,7 +64,7 @@ jobs:
     - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.20.x'
       uses: dominikh/staticcheck-action@v1
       with:
-        version: "2023.1.2"
+        version: "2023.1.3"
         install-go: false
 
   # We don't care about GOARCH=386 particularly,
@@ -84,7 +88,7 @@ jobs:
     steps:
     - name: Install Go
       env:
-        GO_COMMIT: 70f98a251efdbfd619c4ff466a43da299ad04752 # 2023-03-11
+        GO_COMMIT: 231f290e51e130a1699d5c29d28133d68f43d2e9 # 2023-04-08
       run: |
         cd $HOME
         mkdir $HOME/gotip
diff --git a/main.go b/main.go
index 24baa1a..44520e3 100644
--- a/main.go
+++ b/main.go
@@ -260,11 +260,6 @@ type errJustExit int
 
 func (e errJustExit) Error() string { return fmt.Sprintf("exit: %d", e) }
 
-// toolchainVersionSemver is a semver-compatible version of the Go toolchain currently
-// being used, as reported by "go env GOVERSION".
-// Note that the version of Go that built the garble binary might be newer.
-var toolchainVersionSemver string
-
 func goVersionOK() bool {
 	const (
 		minGoVersionSemver = "v1.20.0"
@@ -275,7 +270,7 @@ func goVersionOK() bool {
 	rxVersion := regexp.MustCompile(`go\d+\.\d+(?:\.\d+)?`)
 
 	toolchainVersionFull := cache.GoEnv.GOVERSION
-	toolchainVersion := rxVersion.FindString(cache.GoEnv.GOVERSION)
+	toolchainVersion := rxVersion.FindString(toolchainVersionFull)
 	if toolchainVersion == "" {
 		// Go 1.15.x and older do not have GOVERSION yet.
 		// We could go the extra mile and fetch it via 'go toolchainVersion',
@@ -284,14 +279,14 @@ func goVersionOK() bool {
 		return false
 	}
 
-	toolchainVersionSemver = "v" + strings.TrimPrefix(toolchainVersion, "go")
-	if semver.Compare(toolchainVersionSemver, minGoVersionSemver) < 0 {
+	cache.GoVersionSemver = "v" + strings.TrimPrefix(toolchainVersion, "go")
+	if semver.Compare(cache.GoVersionSemver, minGoVersionSemver) < 0 {
 		fmt.Fprintf(os.Stderr, "Go version %q is too old; please upgrade to Go %s or newer\n", toolchainVersionFull, suggestedGoVersion)
 		return false
 	}
 
 	// Ensure that the version of Go that built the garble binary is equal or
-	// newer than toolchainVersionSemver.
+	// newer than cache.GoVersionSemver.
 	builtVersionFull := os.Getenv("GARBLE_TEST_GOVERSION")
 	if builtVersionFull == "" {
 		builtVersionFull = runtime.Version()
@@ -303,7 +298,7 @@ func goVersionOK() bool {
 		return true
 	}
 	builtVersionSemver := "v" + strings.TrimPrefix(builtVersion, "go")
-	if semver.Compare(builtVersionSemver, toolchainVersionSemver) < 0 {
+	if semver.Compare(builtVersionSemver, cache.GoVersionSemver) < 0 {
 		fmt.Fprintf(os.Stderr, "garble was built with %q and is being used with %q; please rebuild garble with the newer version\n",
 			builtVersionFull, toolchainVersionFull)
 		return false
diff --git a/runtime_patch.go b/runtime_patch.go
index a7a77a5..d53539f 100644
--- a/runtime_patch.go
+++ b/runtime_patch.go
@@ -9,6 +9,8 @@ import (
 	"strconv"
 	"strings"
 
+	"golang.org/x/mod/semver"
+
 	ah "mvdan.cc/garble/internal/asthelper"
 )
 
@@ -236,7 +238,11 @@ func stripRuntime(basename string, file *ast.File) {
 				"printAncestorTracebackFuncInfo", "goroutineheader", "tracebackothers", "tracebackHexdump", "printCgoTraceback":
 				funcDecl.Body.List = nil
 			case "printOneCgoTraceback":
-				funcDecl.Body = ah.BlockStmt(ah.ReturnStmt(ah.IntLit(0)))
+				if semver.Compare(cache.GoVersionSemver, "v1.21") >= 0 {
+					funcDecl.Body = ah.BlockStmt(ah.ReturnStmt(ast.NewIdent("false")))
+				} else {
+					funcDecl.Body = ah.BlockStmt(ah.ReturnStmt(ah.IntLit(0)))
+				}
 			default:
 				if strings.HasPrefix(funcDecl.Name.Name, "print") {
 					funcDecl.Body.List = nil
diff --git a/shared.go b/shared.go
index 2571a0d..c7f1e46 100644
--- a/shared.go
+++ b/shared.go
@@ -46,6 +46,13 @@ type sharedCache struct {
 
 	GOGARBLE string
 
+	// GoVersionSemver is a semver-compatible version of the Go toolchain
+	// currently being used, as reported by "go env GOVERSION".
+	// Note that the version of Go that built the garble binary might be newer.
+	// Also note that a devel version like "go1.21-231f290e51" is
+	// currently represented as "v1.21".
+	GoVersionSemver string
+
 	// Filled directly from "go env".
 	// Keep in sync with fetchGoEnv.
 	GoEnv struct {