diff --git a/terraform/context.go b/terraform/context.go
index e2db6e6f9..62a06f431 100644
--- a/terraform/context.go
+++ b/terraform/context.go
@@ -16,9 +16,12 @@ import (
 type InputMode byte
 
 const (
-	// InputModeVar asks for variables
+	// InputModeVar asks for all variables
 	InputModeVar InputMode = 1 << iota
 
+	// InputModeVarUnset asks for variables which are not set yet
+	InputModeVarUnset
+
 	// InputModeProvider asks for provider variables
 	InputModeProvider
 
@@ -154,6 +157,14 @@ func (c *Context) Input(mode InputMode) error {
 		}
 		sort.Strings(names)
 		for _, n := range names {
+			// If we only care about unset variables, then if the variabel
+			// is set, continue on.
+			if mode&InputModeVarUnset != 0 {
+				if _, ok := c.variables[n]; ok {
+					continue
+				}
+			}
+
 			v := m[n]
 			switch v.Type() {
 			case config.VariableTypeMap:
@@ -365,6 +376,21 @@ func (c *Context) Validate() ([]string, []error) {
 	return walker.ValidationWarnings, rerrs.Errors
 }
 
+<<<<<<< Updated upstream
+=======
+// Variables will return the mapping of variables that were defined
+// for this Context. If Input was called, this mapping may be different
+// than what was given.
+func (c *Context) Variables() map[string]string {
+	return c.variables
+}
+
+// SetVariable sets a variable after a context has already been built.
+func (c *Context) SetVariable(k, v string) {
+	c.variables[k] = v
+}
+
+>>>>>>> Stashed changes
 func (c *Context) acquireRun() chan<- struct{} {
 	c.l.Lock()
 	defer c.l.Unlock()
diff --git a/terraform/context_test.go b/terraform/context_test.go
index 9050d4b96..c6dd83b94 100644
--- a/terraform/context_test.go
+++ b/terraform/context_test.go
@@ -2758,6 +2758,48 @@ func TestContext2Input_varOnly(t *testing.T) {
 	}
 }
 
+func TestContext2Input_varOnlyUnset(t *testing.T) {
+	input := new(MockUIInput)
+	m := testModule(t, "input-vars-unset")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		Variables: map[string]string{
+			"foo": "foovalue",
+		},
+		UIInput: input,
+	})
+
+	input.InputReturnMap = map[string]string{
+		"var.foo": "nope",
+		"var.bar": "baz",
+	}
+
+	if err := ctx.Input(InputModeVar | InputModeVarUnset); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if _, err := ctx.Plan(nil); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actualStr := strings.TrimSpace(state.String())
+	expectedStr := strings.TrimSpace(testTerraformInputVarOnlyUnsetStr)
+	if actualStr != expectedStr {
+		t.Fatalf("bad: \n%s", actualStr)
+	}
+}
+
 func TestContext2Apply(t *testing.T) {
 	m := testModule(t, "apply-good")
 	p := testProvider("aws")
diff --git a/terraform/terraform_test.go b/terraform/terraform_test.go
index 94664791f..b3c0f9529 100644
--- a/terraform/terraform_test.go
+++ b/terraform/terraform_test.go
@@ -150,6 +150,14 @@ aws_instance.foo:
   type = aws_instance
 `
 
+const testTerraformInputVarOnlyUnsetStr = `
+aws_instance.foo:
+  ID = foo
+  bar = baz
+  foo = foovalue
+  type = aws_instance
+`
+
 const testTerraformInputVarsStr = `
 aws_instance.bar:
   ID = foo
diff --git a/terraform/test-fixtures/input-vars-unset/main.tf b/terraform/test-fixtures/input-vars-unset/main.tf
new file mode 100644
index 000000000..28cf230e6
--- /dev/null
+++ b/terraform/test-fixtures/input-vars-unset/main.tf
@@ -0,0 +1,7 @@
+variable "foo" {}
+variable "bar" {}
+
+resource "aws_instance" "foo" {
+    foo = "${var.foo}"
+    bar = "${var.bar}"
+}