diff --git a/lib/rdf/graph.ex b/lib/rdf/graph.ex
index 9ffa005..2410307 100644
--- a/lib/rdf/graph.ex
+++ b/lib/rdf/graph.ex
@@ -753,6 +753,8 @@ defmodule RDF.Graph do
 
   @doc """
   Sets the base IRI of the given `graph`.
+
+  The `base_iri` can be given as anything accepted by `RDF.IRI.coerce_base/1`.
   """
   def set_base_iri(graph, base_iri)
 
@@ -761,7 +763,7 @@ defmodule RDF.Graph do
   end
 
   def set_base_iri(%RDF.Graph{} = graph, base_iri) do
-    %RDF.Graph{graph | base_iri: RDF.IRI.new(base_iri)}
+    %RDF.Graph{graph | base_iri: RDF.IRI.coerce_base(base_iri)}
   end
 
   @doc """
diff --git a/test/unit/graph_test.exs b/test/unit/graph_test.exs
index 9c3cc42..25b6e8d 100644
--- a/test/unit/graph_test.exs
+++ b/test/unit/graph_test.exs
@@ -544,11 +544,16 @@ defmodule RDF.GraphTest do
       assert graph.base_iri == ~I<http://example.com/>
     end
 
-    test "when given a vocabulary namespace atom" do
+    test "when given a term atom under a vocabulary namespace" do
       graph = Graph.new() |> Graph.set_base_iri(EX.Base)
       assert graph.base_iri == RDF.iri(EX.Base)
     end
 
+    test "when given a vocabulary namespace module" do
+      graph = Graph.new() |> Graph.set_base_iri(EX)
+      assert graph.base_iri == RDF.iri(EX.__base_iri__)
+    end
+
     test "when given nil" do
       graph = Graph.new() |> Graph.set_base_iri(nil)
       assert graph.base_iri == nil