diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 228be07f24..187295b345 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -1178,6 +1178,44 @@ var cgoSyscallExclude = map[string]bool{
 
 var foldPath = make(map[string]string)
 
+// DefaultExecName returns the default executable name of the given
+// package.
+func DefaultExecName(p *Package) string {
+	_, elem := filepath.Split(p.ImportPath)
+	if cfg.ModulesEnabled {
+		// NOTE(rsc): Using p.ImportPath instead of p.Dir
+		// makes sure we install a package in the root of a
+		// cached module directory as that package name
+		// not name@v1.2.3.
+		// Using p.ImportPath instead of p.Dir
+		// is probably correct all the time,
+		// even for non-module-enabled code,
+		// but I'm not brave enough to change the
+		// non-module behavior this late in the
+		// release cycle. Maybe for Go 1.12.
+		// See golang.org/issue/26869.
+		_, elem = pathpkg.Split(p.ImportPath)
+
+		// If this is example.com/mycmd/v2, it's more useful to install it as mycmd than as v2.
+		// See golang.org/issue/24667.
+		isVersion := func(v string) bool {
+			if len(v) < 2 || v[0] != 'v' || v[1] < '1' || '9' < v[1] {
+				return false
+			}
+			for i := 2; i < len(v); i++ {
+				if c := v[i]; c < '0' || '9' < c {
+					return false
+				}
+			}
+			return true
+		}
+		if isVersion(elem) {
+			_, elem = pathpkg.Split(pathpkg.Dir(p.ImportPath))
+		}
+	}
+	return elem
+}
+
 // load populates p using information from bp, err, which should
 // be the result of calling build.Context.Import.
 func (p *Package) load(stk *ImportStack, bp *build.Package, err error) {
@@ -1218,38 +1256,7 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) {
 			p.Error = &PackageError{Err: e}
 			return
 		}
-		_, elem := filepath.Split(p.Dir)
-		if cfg.ModulesEnabled {
-			// NOTE(rsc): Using p.ImportPath instead of p.Dir
-			// makes sure we install a package in the root of a
-			// cached module directory as that package name
-			// not name@v1.2.3.
-			// Using p.ImportPath instead of p.Dir
-			// is probably correct all the time,
-			// even for non-module-enabled code,
-			// but I'm not brave enough to change the
-			// non-module behavior this late in the
-			// release cycle. Maybe for Go 1.12.
-			// See golang.org/issue/26869.
-			_, elem = pathpkg.Split(p.ImportPath)
-
-			// If this is example.com/mycmd/v2, it's more useful to install it as mycmd than as v2.
-			// See golang.org/issue/24667.
-			isVersion := func(v string) bool {
-				if len(v) < 2 || v[0] != 'v' || v[1] < '1' || '9' < v[1] {
-					return false
-				}
-				for i := 2; i < len(v); i++ {
-					if c := v[i]; c < '0' || '9' < c {
-						return false
-					}
-				}
-				return true
-			}
-			if isVersion(elem) {
-				_, elem = pathpkg.Split(pathpkg.Dir(p.ImportPath))
-			}
-		}
+		elem := DefaultExecName(p)
 		full := cfg.BuildContext.GOOS + "_" + cfg.BuildContext.GOARCH + "/" + elem
 		if cfg.BuildContext.GOOS != base.ToolGOOS || cfg.BuildContext.GOARCH != base.ToolGOARCH {
 			// Install cross-compiled binaries to subdirectories of bin.
diff --git a/src/cmd/go/internal/test/test.go b/src/cmd/go/internal/test/test.go
index 8dfb3df22d..2eca627c9a 100644
--- a/src/cmd/go/internal/test/test.go
+++ b/src/cmd/go/internal/test/test.go
@@ -805,7 +805,7 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 	if p.ImportPath == "command-line-arguments" {
 		elem = p.Name
 	} else {
-		_, elem = path.Split(p.ImportPath)
+		elem = load.DefaultExecName(p)
 	}
 	testBinary := elem + ".test"
 
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index 145b87513a..d89ee899f0 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -10,7 +10,6 @@ import (
 	"go/build"
 	"os"
 	"os/exec"
-	"path"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -285,7 +284,7 @@ func runBuild(cmd *base.Command, args []string) {
 	pkgs := load.PackagesForBuild(args)
 
 	if len(pkgs) == 1 && pkgs[0].Name == "main" && cfg.BuildO == "" {
-		_, cfg.BuildO = path.Split(pkgs[0].ImportPath)
+		cfg.BuildO = load.DefaultExecName(pkgs[0])
 		cfg.BuildO += cfg.ExeSuffix
 	}
 
diff --git a/src/cmd/go/testdata/mod/rsc.io_fortune_v2_v2.0.0.txt b/src/cmd/go/testdata/mod/rsc.io_fortune_v2_v2.0.0.txt
index cfa91f08a5..3acd637931 100644
--- a/src/cmd/go/testdata/mod/rsc.io_fortune_v2_v2.0.0.txt
+++ b/src/cmd/go/testdata/mod/rsc.io_fortune_v2_v2.0.0.txt
@@ -13,3 +13,9 @@ import "rsc.io/quote"
 func main() {
 	println(quote.Hello())
 }
+-- fortune_test.go --
+package main
+
+import "testing"
+
+func TestFortuneV2(t *testing.T) {}
diff --git a/src/cmd/go/testdata/script/mod_build_versioned.txt b/src/cmd/go/testdata/script/mod_build_versioned.txt
new file mode 100644
index 0000000000..eb081c9be1
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_build_versioned.txt
@@ -0,0 +1,16 @@
+env GO111MODULE=on
+
+go get -m rsc.io/fortune/v2
+
+# The default executable name shouldn't be v2$exe
+go build rsc.io/fortune/v2
+! exists v2$exe
+exists fortune$exe
+
+# The default test binary name shouldn't be v2.test$exe
+go test -c rsc.io/fortune/v2
+! exists v2.test$exe
+exists fortune.test$exe
+
+-- go.mod --
+module scratch