diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 9d4626769d6..103eecf79c5 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -198,6 +198,8 @@
 // 		a program to use to invoke toolchain programs like vet and asm.
 // 		For example, instead of running asm, the go command will run
 // 		'cmd args /path/to/asm <arguments for asm>'.
+// 		The TOOLEXEC_IMPORTPATH environment variable will be set,
+// 		matching 'go list -f {{.ImportPath}}' for the package being built.
 //
 // The -asmflags, -gccgoflags, -gcflags, and -ldflags flags accept a
 // space-separated list of arguments to pass to an underlying tool
diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 53bf75e27e0..53aaf311ec4 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -628,7 +628,7 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 		old := make(map[string]string)
 		for _, p := range all {
 			if p.ForTest != "" {
-				new := p.ImportPath + " [" + p.ForTest + ".test]"
+				new := p.Desc()
 				old[new] = p.ImportPath
 				p.ImportPath = new
 			}
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index a75ace7d4e9..1babbda8899 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -152,6 +152,8 @@ and test commands:
 		a program to use to invoke toolchain programs like vet and asm.
 		For example, instead of running asm, the go command will run
 		'cmd args /path/to/asm <arguments for asm>'.
+		The TOOLEXEC_IMPORTPATH environment variable will be set,
+		matching 'go list -f {{.ImportPath}}' for the package being built.
 
 The -asmflags, -gccgoflags, -gcflags, and -ldflags flags accept a
 space-separated list of arguments to pass to an underlying tool
diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index 38e826607e2..d04ba069013 100644
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -2071,8 +2071,11 @@ func (b *Builder) runOut(a *Action, dir string, env []string, cmdargs ...interfa
 
 	// Add the TOOLEXEC_IMPORTPATH environment variable for -toolexec tools.
 	// It doesn't really matter if -toolexec isn't being used.
+	// Note that a.Package.Desc is not really an import path,
+	// but this is consistent with 'go list -f {{.ImportPath}}'.
+	// Plus, it is useful to uniquely identify packages in 'go list -json'.
 	if a != nil && a.Package != nil {
-		cmd.Env = append(cmd.Env, "TOOLEXEC_IMPORTPATH="+a.Package.ImportPath)
+		cmd.Env = append(cmd.Env, "TOOLEXEC_IMPORTPATH="+a.Package.Desc())
 	}
 
 	cmd.Env = append(cmd.Env, env...)
diff --git a/src/cmd/go/testdata/script/toolexec.txt b/src/cmd/go/testdata/script/toolexec.txt
index 526234196b5..4f26da6d26b 100644
--- a/src/cmd/go/testdata/script/toolexec.txt
+++ b/src/cmd/go/testdata/script/toolexec.txt
@@ -11,12 +11,37 @@ go build ./cmd/mytool
 # Finally, note that asm and cgo are run twice.
 
 go build -toolexec=$PWD/mytool
-[amd64] stderr -count=2 '^asm'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main/withasm$'
-stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main/withasm$'
-[cgo] stderr -count=2 '^cgo'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main/withcgo$'
-[cgo] stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main/withcgo$'
-stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main$'
-stderr -count=1 '^link'${GOEXE}' TOOLEXEC_IMPORTPATH=test/main$'
+[amd64] stderr -count=2 '^asm'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main/withasm"$'
+stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main/withasm"$'
+[cgo] stderr -count=2 '^cgo'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main/withcgo"$'
+[cgo] stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main/withcgo"$'
+stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main"$'
+stderr -count=1 '^link'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main"$'
+
+# Test packages are a little bit trickier.
+# We have four variants of test/main, as reported by 'go list -test':
+#
+#    test/main                        - the regular non-test package
+#    test/main.test                   - the generated test program
+#    test/main [test/main.test]       - the test package for foo_test.go
+#    test/main_test [test/main.test]  - the test package for foo_separate_test.go
+#
+# As such, TOOLEXEC_IMPORTPATH must see the same strings, to be able to uniquely
+# identify each package being built as reported by 'go list -f {{.ImportPath}}'.
+# Note that these are not really "import paths" anymore, but that naming is
+# consistent with 'go list -json' at least.
+
+go test -toolexec=$PWD/mytool
+
+stderr -count=2 '^# test/main\.test$'
+stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main\.test"$'
+stderr -count=1 '^link'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main\.test"$'
+
+stderr -count=1 '^# test/main \[test/main\.test\]$'
+stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main \[test/main\.test\]"$'
+
+stderr -count=1 '^# test/main_test \[test/main\.test\]$'
+stderr -count=1 '^compile'${GOEXE}' TOOLEXEC_IMPORTPATH="test/main_test \[test/main\.test\]"$'
 
 -- go.mod --
 module test/main
@@ -32,6 +57,18 @@ import (
 )
 
 func main() {}
+-- foo_test.go --
+package main
+
+import "testing"
+
+func TestFoo(t *testing.T) {}
+-- foo_separate_test.go --
+package main_test
+
+import "testing"
+
+func TestSeparateFoo(t *testing.T) {}
 -- withcgo/withcgo.go --
 package withcgo
 
@@ -71,7 +108,7 @@ func main() {
 		// We can't alter the version output.
 	} else {
 		// Print which tool we're running, and on what package.
-		fmt.Fprintf(os.Stdout, "%s TOOLEXEC_IMPORTPATH=%s\n", toolName, os.Getenv("TOOLEXEC_IMPORTPATH"))
+		fmt.Fprintf(os.Stdout, "%s TOOLEXEC_IMPORTPATH=%q\n", toolName, os.Getenv("TOOLEXEC_IMPORTPATH"))
 	}
 
 	// Simply run the tool.