diff --git a/cmd/dep/ensure.go b/cmd/dep/ensure.go
index 60d9c7659e..b90ba975b4 100644
--- a/cmd/dep/ensure.go
+++ b/cmd/dep/ensure.go
@@ -162,6 +162,10 @@ func (cmd *ensureCommand) Run(ctx *dep.Ctx, args []string) error {
 		params.TraceLogger = ctx.Err
 	}
 
+	if cmd.vendorOnly {
+		return cmd.runVendorOnly(ctx, args, p, sm, params)
+	}
+
 	params.RootPackageTree, err = pkgtree.ListPackages(p.ResolvedAbsRoot, string(p.ImportRoot))
 	if err != nil {
 		return errors.Wrap(err, "ensure ListPackage for project")
@@ -202,31 +206,9 @@ func (cmd *ensureCommand) validateFlags() error {
 func (cmd *ensureCommand) runDefault(ctx *dep.Ctx, args []string, p *dep.Project, sm gps.SourceManager, params gps.SolveParameters) error {
 	// Bare ensure doesn't take any args.
 	if len(args) != 0 {
-		if cmd.vendorOnly {
-			return errors.Errorf("dep ensure -vendor-only only populates vendor/ from %s; it takes no spec arguments", dep.LockName)
-		}
 		return errors.New("dep ensure only takes spec arguments with -add or -update")
 	}
 
-	if cmd.vendorOnly {
-		if p.Lock == nil {
-			return errors.Errorf("no %s exists from which to populate vendor/", dep.LockName)
-		}
-		// Pass the same lock as old and new so that the writer will observe no
-		// difference and choose not to write it out.
-		sw, err := dep.NewSafeWriter(nil, p.Lock, p.Lock, dep.VendorAlways)
-		if err != nil {
-			return err
-		}
-
-		if cmd.dryRun {
-			ctx.Out.Printf("Would have populated vendor/ directory from %s", dep.LockName)
-			return nil
-		}
-
-		return errors.WithMessage(sw.Write(p.AbsRoot, sm, true), "grouped write of manifest, lock and vendor")
-	}
-
 	solver, err := gps.Prepare(params, sm)
 	if err != nil {
 		return errors.Wrap(err, "prepare solver")
@@ -279,6 +261,29 @@ func (cmd *ensureCommand) runDefault(ctx *dep.Ctx, args []string, p *dep.Project
 	return errors.Wrap(sw.Write(p.AbsRoot, sm, false), "grouped write of manifest, lock and vendor")
 }
 
+func (cmd *ensureCommand) runVendorOnly(ctx *dep.Ctx, args []string, p *dep.Project, sm gps.SourceManager, params gps.SolveParameters) error {
+	if len(args) != 0 {
+		return errors.Errorf("dep ensure -vendor-only only populates vendor/ from %s; it takes no spec arguments", dep.LockName)
+	}
+
+	if p.Lock == nil {
+		return errors.Errorf("no %s exists from which to populate vendor/", dep.LockName)
+	}
+	// Pass the same lock as old and new so that the writer will observe no
+	// difference and choose not to write it out.
+	sw, err := dep.NewSafeWriter(nil, p.Lock, p.Lock, dep.VendorAlways)
+	if err != nil {
+		return err
+	}
+
+	if cmd.dryRun {
+		ctx.Out.Printf("Would have populated vendor/ directory from %s", dep.LockName)
+		return nil
+	}
+
+	return errors.WithMessage(sw.Write(p.AbsRoot, sm, true), "grouped write of manifest, lock and vendor")
+}
+
 func (cmd *ensureCommand) runUpdate(ctx *dep.Ctx, args []string, p *dep.Project, sm gps.SourceManager, params gps.SolveParameters) error {
 	if p.Lock == nil {
 		return errors.Errorf("-update works by updating the versions recorded in %s, but %s does not exist", dep.LockName, dep.LockName)
diff --git a/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.lock b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.lock
new file mode 100644
index 0000000000..11cb12c378
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.lock
@@ -0,0 +1,16 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/sdboyer/deptest"
+  packages = ["."]
+  revision = "ff2948a2ac8f538c4ecd55962e919d1e13e74baf"
+  version = "v1.0.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  # manually modified hash digest, it will not match any known inputs
+  inputs-digest = "94b07b05e0f01051b03887ab2bf80b516bc5510ea92f75f76c894b1745d8850c"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.toml b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.toml
new file mode 100644
index 0000000000..e242e02114
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/final/Gopkg.toml
@@ -0,0 +1,4 @@
+
+[[constraint]]
+  name = "github.com/sdboyer/deptest"
+  version = "1.0.0"
diff --git a/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.lock b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.lock
new file mode 100644
index 0000000000..11cb12c378
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.lock
@@ -0,0 +1,16 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/sdboyer/deptest"
+  packages = ["."]
+  revision = "ff2948a2ac8f538c4ecd55962e919d1e13e74baf"
+  version = "v1.0.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  # manually modified hash digest, it will not match any known inputs
+  inputs-digest = "94b07b05e0f01051b03887ab2bf80b516bc5510ea92f75f76c894b1745d8850c"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.toml b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.toml
new file mode 100644
index 0000000000..e242e02114
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/initial/Gopkg.toml
@@ -0,0 +1,4 @@
+
+[[constraint]]
+  name = "github.com/sdboyer/deptest"
+  version = "1.0.0"
diff --git a/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/testcase.json b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/testcase.json
new file mode 100644
index 0000000000..8a28875978
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/default/nocode-vendoronly/testcase.json
@@ -0,0 +1,8 @@
+{
+  "commands": [
+    ["ensure", "-vendor-only"]
+  ],
+  "vendor-final": [
+    "github.com/sdboyer/deptest"
+  ]
+}