diff --git a/go/packages/golist_fallback.go b/go/packages/golist_fallback.go
index ca08cf7e13e..141fa19ac19 100644
--- a/go/packages/golist_fallback.go
+++ b/go/packages/golist_fallback.go
@@ -89,11 +89,7 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 					return "", err
 				}
 			}
-			// Add a "go-build" component to the path to make the tests think the files are in the cache.
-			// This allows the same test to test the pre- and post-Go 1.11 go list logic because the Go 1.11
-			// go list generates test mains in the cache, and the test code knows not to rely on paths in the
-			// cache to stay stable.
-			outdir = filepath.Join(tmpdir, "go-build", strings.Replace(p.ImportPath, "/", "_", -1))
+			outdir = filepath.Join(tmpdir, strings.Replace(p.ImportPath, "/", "_", -1))
 			if err := os.MkdirAll(outdir, 0755); err != nil {
 				outdir = ""
 				return "", err
@@ -200,7 +196,11 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 					})
 					return
 				}
-				testmain := filepath.Join(outdir, "testmain.go")
+				// Don't use a .go extension on the file, so that the tests think the file is inside GOCACHE.
+				// This allows the same test to test the pre- and post-Go 1.11 go list logic because the Go 1.11
+				// go list generates test mains in the cache, and the test code knows not to rely on paths in the
+				// cache to stay stable.
+				testmain := filepath.Join(outdir, "testmain-go")
 				extraimports, extradeps, err := generateTestmain(testmain, testPkg, xtestPkg)
 				if err != nil {
 					testmainPkg.Errors = append(testmainPkg.Errors, Error{
diff --git a/go/packages/packages_test.go b/go/packages/packages_test.go
index 3ef87ffa22f..bf7f1da770d 100644
--- a/go/packages/packages_test.go
+++ b/go/packages/packages_test.go
@@ -1413,19 +1413,19 @@ func testJSON(t *testing.T, exporter packagestest.Exporter) {
 		ID:   "golang.org/fake/b",
 		Name: "b",
 		Imports: map[string]*packages.Package{
-			"golang.org/fake/a": &packages.Package{ID: "golang.org/fake/a"},
+			"golang.org/fake/a": {ID: "golang.org/fake/a"},
 		},
 	}, {
 		ID:   "golang.org/fake/c",
 		Name: "c",
 		Imports: map[string]*packages.Package{
-			"golang.org/fake/b": &packages.Package{ID: "golang.org/fake/b"},
+			"golang.org/fake/b": {ID: "golang.org/fake/b"},
 		},
 	}, {
 		ID:   "golang.org/fake/d",
 		Name: "d",
 		Imports: map[string]*packages.Package{
-			"golang.org/fake/b": &packages.Package{ID: "golang.org/fake/b"},
+			"golang.org/fake/b": {ID: "golang.org/fake/b"},
 		},
 	}} {
 		got := decoded[i]
@@ -1646,12 +1646,13 @@ func srcs(p *packages.Package) []string {
 func cleanPaths(paths []string) []string {
 	result := make([]string, len(paths))
 	for i, src := range paths {
-		// The default location for cache data is a subdirectory named go-build
-		// in the standard user cache directory for the current operating system.
-		if strings.Contains(filepath.ToSlash(src), "/go-build/") {
+		// If the source file doesn't have an extension like .go or .s,
+		// it comes from GOCACHE. The names there aren't predictable.
+		name := filepath.Base(src)
+		if !strings.Contains(name, ".") {
 			result[i] = fmt.Sprintf("%d.go", i) // make cache names predictable
 		} else {
-			result[i] = filepath.Base(src)
+			result[i] = name
 		}
 	}
 	return result