diff --git a/internal/stacks/stackconfig/config.go b/internal/stacks/stackconfig/config.go
index 88e67d6361..b369e0c753 100644
--- a/internal/stacks/stackconfig/config.go
+++ b/internal/stacks/stackconfig/config.go
@@ -27,6 +27,12 @@ const maxEmbeddedStackNesting = 20
 // so on for arbitrary levels of nesting.
 type Config struct {
 	Root *ConfigNode
+
+	// Sources is the source bundle that the configuration was loaded from.
+	//
+	// This is also the source bundle that any Terraform modules used by
+	// components should be loaded from.
+	Sources *sourcebundle.Bundle
 }
 
 // ConfigNode represents a node in a tree of stacks that are to be planned and
@@ -66,7 +72,8 @@ func LoadConfigDir(sourceAddr sourceaddrs.FinalSource, sources *sourcebundle.Bun
 	}
 
 	ret := &Config{
-		Root: rootNode,
+		Root:    rootNode,
+		Sources: sources,
 	}
 
 	// Before we return we need to walk the tree and resolve all of the
diff --git a/internal/stacks/stackruntime/internal/stackeval/stack.go b/internal/stacks/stackruntime/internal/stackeval/stack.go
index d5cb196f1c..ce1dfac734 100644
--- a/internal/stacks/stackruntime/internal/stackeval/stack.go
+++ b/internal/stacks/stackruntime/internal/stackeval/stack.go
@@ -198,6 +198,7 @@ func (s *Stack) InputsType(ctx context.Context) (cty.Type, *typeexpr.Defaults) {
 		atys[vAddr.Name] = cfg.TypeConstraint()
 		if def := cfg.DefaultValue(ctx); def != cty.NilVal {
 			defs.DefaultValues[vAddr.Name] = def
+			opts = append(opts, vAddr.Name)
 		}
 		if childDefs := cfg.NestedDefaults(); childDefs != nil {
 			defs.Children[vAddr.Name] = childDefs