diff --git a/terraform/context_input_test.go b/terraform/context_input_test.go
index dae45e0d0..08e017b4c 100644
--- a/terraform/context_input_test.go
+++ b/terraform/context_input_test.go
@@ -569,3 +569,26 @@ func TestContext2Input_varPartiallyComputed(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 }
+
+// Module variables weren't being interpolated during the Input walk.
+// https://github.com/hashicorp/terraform/issues/5322
+func TestContext2Input_interpolateVar(t *testing.T) {
+	input := new(MockUIInput)
+
+	m := testModule(t, "input-interpolate-var")
+	p := testProvider("null")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"template": testProviderFuncFixed(p),
+		},
+		UIInput: input,
+	})
+
+	if err := ctx.Input(InputModeStd); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+}
diff --git a/terraform/context_validate_test.go b/terraform/context_validate_test.go
index af8d7d3c4..56de23a36 100644
--- a/terraform/context_validate_test.go
+++ b/terraform/context_validate_test.go
@@ -749,3 +749,57 @@ func TestContext2Validate_varRefFilled(t *testing.T) {
 		t.Fatalf("bad: %#v", value)
 	}
 }
+
+// Module variables weren't being interpolated during Validate phase.
+// related to https://github.com/hashicorp/terraform/issues/5322
+func TestContext2Validate_interpolateVar(t *testing.T) {
+	input := new(MockUIInput)
+
+	m := testModule(t, "input-interpolate-var")
+	p := testProvider("null")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"template": testProviderFuncFixed(p),
+		},
+		UIInput: input,
+	})
+
+	w, e := ctx.Validate()
+	if w != nil {
+		t.Log("warnings:", w)
+	}
+	if e != nil {
+		t.Fatal("err:", e)
+	}
+}
+
+// When module vars reference something that is actually computed, this
+// shouldn't cause validation to fail.
+func TestContext2Validate_interpolateComputedModuleVarDef(t *testing.T) {
+	input := new(MockUIInput)
+
+	m := testModule(t, "validate-computed-module-var-ref")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		UIInput: input,
+	})
+
+	w, e := ctx.Validate()
+	if w != nil {
+		t.Log("warnings:", w)
+	}
+	if e != nil {
+		t.Fatal("err:", e)
+	}
+}
diff --git a/terraform/eval_context_builtin.go b/terraform/eval_context_builtin.go
index 4dff93a4c..d85cb77fc 100644
--- a/terraform/eval_context_builtin.go
+++ b/terraform/eval_context_builtin.go
@@ -291,6 +291,7 @@ func (ctx *BuiltinEvalContext) Interpolate(
 			Path:     ctx.Path(),
 			Resource: r,
 		}
+
 		vs, err := ctx.Interpolater.Values(scope, cfg.Variables)
 		if err != nil {
 			return nil, err
diff --git a/terraform/eval_interpolate.go b/terraform/eval_interpolate.go
index 063473079..6825ff590 100644
--- a/terraform/eval_interpolate.go
+++ b/terraform/eval_interpolate.go
@@ -1,8 +1,6 @@
 package terraform
 
-import (
-	"github.com/hashicorp/terraform/config"
-)
+import "github.com/hashicorp/terraform/config"
 
 // EvalInterpolate is an EvalNode implementation that takes a raw
 // configuration and interpolates it.
diff --git a/terraform/graph_config_node_output.go b/terraform/graph_config_node_output.go
index 8410102d2..0704a0cb7 100644
--- a/terraform/graph_config_node_output.go
+++ b/terraform/graph_config_node_output.go
@@ -44,7 +44,8 @@ func (n *GraphNodeConfigOutput) DependentOn() []string {
 // GraphNodeEvalable impl.
 func (n *GraphNodeConfigOutput) EvalTree() EvalNode {
 	return &EvalOpFilter{
-		Ops: []walkOperation{walkRefresh, walkPlan, walkApply, walkDestroy},
+		Ops: []walkOperation{walkRefresh, walkPlan, walkApply,
+			walkDestroy, walkInput, walkValidate},
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
 				&EvalWriteOutput{
diff --git a/terraform/interpolate.go b/terraform/interpolate.go
index 0a627aca6..2d3c57c5b 100644
--- a/terraform/interpolate.go
+++ b/terraform/interpolate.go
@@ -129,15 +129,6 @@ func (i *Interpolater) valueModuleVar(
 	n string,
 	v *config.ModuleVariable,
 	result map[string]ast.Variable) error {
-	// If we're computing all dynamic fields, then module vars count
-	// and we mark it as computed.
-	if i.Operation == walkValidate {
-		result[n] = ast.Variable{
-			Value: config.UnknownVariableValue,
-			Type:  ast.TypeString,
-		}
-		return nil
-	}
 
 	// Build the path to the child module we want
 	path := make([]string, len(scope.Path), len(scope.Path)+1)
diff --git a/terraform/test-fixtures/input-interpolate-var/child/main.tf b/terraform/test-fixtures/input-interpolate-var/child/main.tf
new file mode 100644
index 000000000..9a2ff39cc
--- /dev/null
+++ b/terraform/test-fixtures/input-interpolate-var/child/main.tf
@@ -0,0 +1,5 @@
+variable "list" { }
+resource "template_file" "temp" {
+  count     = "${length(split(",", var.list))}"
+  template  = "foo"
+}
diff --git a/terraform/test-fixtures/input-interpolate-var/main.tf b/terraform/test-fixtures/input-interpolate-var/main.tf
new file mode 100644
index 000000000..ae6cf627f
--- /dev/null
+++ b/terraform/test-fixtures/input-interpolate-var/main.tf
@@ -0,0 +1,7 @@
+module "source" {
+  source = "./source"
+}
+module "child" {
+  source  = "./child"
+  list = "${module.source.list}"
+}
diff --git a/terraform/test-fixtures/input-interpolate-var/source/main.tf b/terraform/test-fixtures/input-interpolate-var/source/main.tf
new file mode 100644
index 000000000..fb7b33fb3
--- /dev/null
+++ b/terraform/test-fixtures/input-interpolate-var/source/main.tf
@@ -0,0 +1 @@
+output "list" { value = "foo,bar,baz" }
diff --git a/terraform/test-fixtures/validate-computed-module-var-ref/dest/main.tf b/terraform/test-fixtures/validate-computed-module-var-ref/dest/main.tf
new file mode 100644
index 000000000..44095ea75
--- /dev/null
+++ b/terraform/test-fixtures/validate-computed-module-var-ref/dest/main.tf
@@ -0,0 +1,5 @@
+variable "destin" { }
+
+resource "aws_instance" "dest" {
+  attr = "${var.destin}"
+}
diff --git a/terraform/test-fixtures/validate-computed-module-var-ref/main.tf b/terraform/test-fixtures/validate-computed-module-var-ref/main.tf
new file mode 100644
index 000000000..d7c799cc8
--- /dev/null
+++ b/terraform/test-fixtures/validate-computed-module-var-ref/main.tf
@@ -0,0 +1,8 @@
+module "source" {
+  source = "./source"
+}
+
+module "dest" {
+  source = "./dest"
+  destin = "${module.source.sourceout}"
+}
diff --git a/terraform/test-fixtures/validate-computed-module-var-ref/source/main.tf b/terraform/test-fixtures/validate-computed-module-var-ref/source/main.tf
new file mode 100644
index 000000000..f923e8080
--- /dev/null
+++ b/terraform/test-fixtures/validate-computed-module-var-ref/source/main.tf
@@ -0,0 +1,3 @@
+resource "aws_instance" "source" { }
+
+output "sourceout" { value = "${aws_instance.source.id}" }