diff --git a/pimgen.py b/pimgen.py
index 8e12944..95d9b72 100755
--- a/pimgen.py
+++ b/pimgen.py
@@ -49,9 +49,21 @@
             for e in yaml.load(fd.read()).get('events', {}):
                 events.append(parse_event(e))
 
-    # Import interfaces.yaml.
-    with open(os.path.join(args.inputdir, 'interfaces.yaml'), 'r') as fd:
-        interfaces = yaml.load(fd.read())
+    # Aggregate all the interface YAML in the interfaces.d
+    # directory into a single list of interfaces.
+    template = os.path.join(script_dir, 'generated.mako.cpp')
+    t = Template(filename=template)
+
+    interfaces_dir = os.path.join(args.inputdir, 'interfaces.d')
+    yaml_files = filter(
+        lambda x: x.endswith('.yaml'),
+        os.listdir(interfaces_dir))
+
+    interfaces = []
+    for x in yaml_files:
+        with open(os.path.join(interfaces_dir, x), 'r') as fd:
+            for i in yaml.load(fd.read()):
+                interfaces.append(i)
 
     # Render the template with the provided events and interfaces.
     template = os.path.join(script_dir, 'generated.mako.cpp')