diff --git a/src/cmd/fix/cftype_test.go b/src/cmd/fix/cftype_test.go
index a18eb25261d..cde47f28a3b 100644
--- a/src/cmd/fix/cftype_test.go
+++ b/src/cmd/fix/cftype_test.go
@@ -13,6 +13,7 @@ var cftypeTests = []testCase{
 		Name: "cftype.localVariable",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 func f() {
@@ -23,6 +24,7 @@ func f() {
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 func f() {
@@ -36,6 +38,7 @@ func f() {
 		Name: "cftype.globalVariable",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef = nil
@@ -46,6 +49,7 @@ func f() {
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef = 0
@@ -59,6 +63,7 @@ func f() {
 		Name: "cftype.EqualArgument",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef
@@ -67,6 +72,7 @@ var z = x != nil
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef
@@ -78,6 +84,7 @@ var z = x != 0
 		Name: "cftype.StructField",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 type T struct {
@@ -88,6 +95,7 @@ var t = T{x: nil}
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 type T struct {
@@ -101,6 +109,7 @@ var t = T{x: 0}
 		Name: "cftype.FunctionArgument",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 func f(x C.CFTypeRef) {
@@ -112,6 +121,7 @@ func g() {
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 func f(x C.CFTypeRef) {
@@ -126,12 +136,14 @@ func g() {
 		Name: "cftype.ArrayElement",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = [3]C.CFTypeRef{nil, nil, nil}
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = [3]C.CFTypeRef{0, 0, 0}
@@ -141,12 +153,14 @@ var x = [3]C.CFTypeRef{0, 0, 0}
 		Name: "cftype.SliceElement",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = []C.CFTypeRef{nil, nil, nil}
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = []C.CFTypeRef{0, 0, 0}
@@ -156,12 +170,14 @@ var x = []C.CFTypeRef{0, 0, 0}
 		Name: "cftype.MapKey",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = map[C.CFTypeRef]int{nil: 0}
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = map[C.CFTypeRef]int{0: 0}
@@ -171,12 +187,14 @@ var x = map[C.CFTypeRef]int{0: 0}
 		Name: "cftype.MapValue",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = map[int]C.CFTypeRef{0: nil}
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x = map[int]C.CFTypeRef{0: 0}
@@ -186,6 +204,7 @@ var x = map[int]C.CFTypeRef{0: 0}
 		Name: "cftype.Conversion1",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef
@@ -193,6 +212,7 @@ var y = (*unsafe.Pointer)(&x)
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x C.CFTypeRef
@@ -203,6 +223,7 @@ var y = (*unsafe.Pointer)(unsafe.Pointer(&x))
 		Name: "cftype.Conversion2",
 		In: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x unsafe.Pointer
@@ -210,6 +231,7 @@ var y = (*C.CFTypeRef)(&x)
 `,
 		Out: `package main
 
+// typedef const void *CFTypeRef;
 import "C"
 
 var x unsafe.Pointer
diff --git a/src/cmd/fix/egltype_test.go b/src/cmd/fix/egltype_test.go
index 9b64a7c20b4..c44525c0539 100644
--- a/src/cmd/fix/egltype_test.go
+++ b/src/cmd/fix/egltype_test.go
@@ -17,6 +17,7 @@ func eglTestsFor(tname string) []testCase {
 			Name: "egl.localVariable",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 func f() {
@@ -27,6 +28,7 @@ func f() {
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 func f() {
@@ -40,6 +42,7 @@ func f() {
 			Name: "egl.globalVariable",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x C.$EGLTYPE = nil
@@ -50,6 +53,7 @@ func f() {
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x C.$EGLTYPE = 0
@@ -63,6 +67,7 @@ func f() {
 			Name: "egl.EqualArgument",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x C.$EGLTYPE
@@ -71,6 +76,7 @@ var z = x != nil
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x C.$EGLTYPE
@@ -82,6 +88,7 @@ var z = x != 0
 			Name: "egl.StructField",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 type T struct {
@@ -92,6 +99,7 @@ var t = T{x: nil}
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 type T struct {
@@ -105,6 +113,7 @@ var t = T{x: 0}
 			Name: "egl.FunctionArgument",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 func f(x C.$EGLTYPE) {
@@ -116,6 +125,7 @@ func g() {
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 func f(x C.$EGLTYPE) {
@@ -130,12 +140,14 @@ func g() {
 			Name: "egl.ArrayElement",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = [3]C.$EGLTYPE{nil, nil, nil}
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = [3]C.$EGLTYPE{0, 0, 0}
@@ -145,12 +157,14 @@ var x = [3]C.$EGLTYPE{0, 0, 0}
 			Name: "egl.SliceElement",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = []C.$EGLTYPE{nil, nil, nil}
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = []C.$EGLTYPE{0, 0, 0}
@@ -160,12 +174,14 @@ var x = []C.$EGLTYPE{0, 0, 0}
 			Name: "egl.MapKey",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = map[C.$EGLTYPE]int{nil: 0}
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = map[C.$EGLTYPE]int{0: 0}
@@ -175,12 +191,14 @@ var x = map[C.$EGLTYPE]int{0: 0}
 			Name: "egl.MapValue",
 			In: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = map[int]C.$EGLTYPE{0: nil}
 `,
 			Out: `package main
 
+// typedef void *$EGLTYPE;
 import "C"
 
 var x = map[int]C.$EGLTYPE{0: 0}
diff --git a/src/cmd/fix/jnitype_test.go b/src/cmd/fix/jnitype_test.go
index a6420f7b11f..ecf01408c7c 100644
--- a/src/cmd/fix/jnitype_test.go
+++ b/src/cmd/fix/jnitype_test.go
@@ -13,6 +13,7 @@ var jniTests = []testCase{
 		Name: "jni.localVariable",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 func f() {
@@ -23,6 +24,7 @@ func f() {
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 func f() {
@@ -36,6 +38,7 @@ func f() {
 		Name: "jni.globalVariable",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x C.jobject = nil
@@ -46,6 +49,7 @@ func f() {
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x C.jobject = 0
@@ -59,6 +63,7 @@ func f() {
 		Name: "jni.EqualArgument",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x C.jobject
@@ -67,6 +72,7 @@ var z = x != nil
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x C.jobject
@@ -78,6 +84,7 @@ var z = x != 0
 		Name: "jni.StructField",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 type T struct {
@@ -88,6 +95,7 @@ var t = T{x: nil}
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 type T struct {
@@ -101,6 +109,7 @@ var t = T{x: 0}
 		Name: "jni.FunctionArgument",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 func f(x C.jobject) {
@@ -112,6 +121,7 @@ func g() {
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 func f(x C.jobject) {
@@ -126,12 +136,14 @@ func g() {
 		Name: "jni.ArrayElement",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = [3]C.jobject{nil, nil, nil}
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = [3]C.jobject{0, 0, 0}
@@ -141,12 +153,14 @@ var x = [3]C.jobject{0, 0, 0}
 		Name: "jni.SliceElement",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = []C.jobject{nil, nil, nil}
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = []C.jobject{0, 0, 0}
@@ -156,12 +170,14 @@ var x = []C.jobject{0, 0, 0}
 		Name: "jni.MapKey",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = map[C.jobject]int{nil: 0}
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = map[C.jobject]int{0: 0}
@@ -171,12 +187,14 @@ var x = map[C.jobject]int{0: 0}
 		Name: "jni.MapValue",
 		In: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = map[int]C.jobject{0: nil}
 `,
 		Out: `package main
 
+// typedef struct _jobject* jobject;
 import "C"
 
 var x = map[int]C.jobject{0: 0}
diff --git a/src/cmd/fix/main_test.go b/src/cmd/fix/main_test.go
index 755007bc0d3..837a5d72c72 100644
--- a/src/cmd/fix/main_test.go
+++ b/src/cmd/fix/main_test.go
@@ -5,13 +5,29 @@
 package main
 
 import (
+	"fmt"
 	"go/ast"
 	"go/parser"
 	"internal/diff"
+	"internal/testenv"
 	"strings"
 	"testing"
 )
 
+func init() {
+	// If cgo is enabled, enforce that cgo commands invoked by cmd/fix
+	// do not fail during testing.
+	if testenv.HasCGO() {
+		// The reportCgoError hook is global, so we can't set it per-test
+		// if we want to be able to run those tests in parallel.
+		// Instead, simply set it to panic on error: the goroutine dump
+		// from the panic should help us determine which test failed.
+		reportCgoError = func(err error) {
+			panic(fmt.Sprintf("unexpected cgo error: %v", err))
+		}
+	}
+}
+
 type testCase struct {
 	Name    string
 	Fn      func(*ast.File) bool
@@ -79,7 +95,13 @@ func TestRewrite(t *testing.T) {
 		tt := tt
 		t.Run(tt.Name, func(t *testing.T) {
 			if tt.Version == 0 {
-				t.Parallel()
+				if testing.Verbose() {
+					// Don't run in parallel: cmd/fix sometimes writes directly to stderr,
+					// and since -v prints which test is currently running we want that
+					// information to accurately correlate with the stderr output.
+				} else {
+					t.Parallel()
+				}
 			} else {
 				old := goVersion
 				goVersion = tt.Version
diff --git a/src/cmd/fix/typecheck.go b/src/cmd/fix/typecheck.go
index 27042e05a55..b115987390c 100644
--- a/src/cmd/fix/typecheck.go
+++ b/src/cmd/fix/typecheck.go
@@ -170,7 +170,16 @@ func typecheck(cfg *TypeConfig, f *ast.File) (typeof map[any]string, assign map[
 			if err != nil {
 				return err
 			}
-			cmd := exec.Command(filepath.Join(runtime.GOROOT(), "bin", "go"), "tool", "cgo", "-objdir", dir, "-srcdir", dir, "in.go")
+			goCmd := "go"
+			if goroot := runtime.GOROOT(); goroot != "" {
+				goCmd = filepath.Join(goroot, "bin", "go")
+			}
+			cmd := exec.Command(goCmd, "tool", "cgo", "-objdir", dir, "-srcdir", dir, "in.go")
+			if reportCgoError != nil {
+				// Since cgo command errors will be reported, also forward the error
+				// output from the command for debugging.
+				cmd.Stderr = os.Stderr
+			}
 			err = cmd.Run()
 			if err != nil {
 				return err
@@ -206,7 +215,11 @@ func typecheck(cfg *TypeConfig, f *ast.File) (typeof map[any]string, assign map[
 			return nil
 		}()
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "go fix: warning: no cgo types: %s\n", err)
+			if reportCgoError == nil {
+				fmt.Fprintf(os.Stderr, "go fix: warning: no cgo types: %s\n", err)
+			} else {
+				reportCgoError(err)
+			}
 		}
 	}
 
@@ -285,6 +298,10 @@ func typecheck(cfg *TypeConfig, f *ast.File) (typeof map[any]string, assign map[
 	return typeof, assign
 }
 
+// reportCgoError, if non-nil, reports a non-nil error from running the "cgo"
+// tool. (Set to a non-nil hook during testing if cgo is expected to work.)
+var reportCgoError func(err error)
+
 func makeExprList(a []*ast.Ident) []ast.Expr {
 	var b []ast.Expr
 	for _, x := range a {