diff --git a/internal/terraform/graph.go b/internal/terraform/graph.go
index 9e2f195531..cc99942093 100644
--- a/internal/terraform/graph.go
+++ b/internal/terraform/graph.go
@@ -82,8 +82,9 @@ func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 			log.Printf("[TRACE] vertex %q: expanding dynamic subgraph", dag.VertexName(v))
 
 			g, err := ev.DynamicExpand(vertexCtx)
-			if err != nil {
-				diags = diags.Append(err)
+			diags = diags.Append(err)
+			if diags.HasErrors() {
+				log.Printf("[TRACE] vertex %q: failed expanding dynamic subgraph: %s", dag.VertexName(v), err)
 				return
 			}
 			if g != nil {
diff --git a/internal/terraform/transform_expand.go b/internal/terraform/transform_expand.go
index dca71b630f..6d9b92aeee 100644
--- a/internal/terraform/transform_expand.go
+++ b/internal/terraform/transform_expand.go
@@ -5,5 +5,13 @@ package terraform
 // These nodes are given the eval context and are expected to return
 // a new subgraph.
 type GraphNodeDynamicExpandable interface {
+	// DynamicExpand returns a new graph which will be treated as the dynamic
+	// subgraph of the receiving node.
+	//
+	// The second return value is of type error for historical reasons;
+	// it's valid (and most ideal) for DynamicExpand to return the result
+	// of calling ErrWithWarnings on a tfdiags.Diagnostics value instead,
+	// in which case the caller will unwrap it and gather the individual
+	// diagnostics.
 	DynamicExpand(EvalContext) (*Graph, error)
 }