diff --git a/update.py b/update.py
index a10d6ea..748b45a 100644
--- a/update.py
+++ b/update.py
@@ -55,45 +55,46 @@ def fetch_modules(config, relative_path, download_directory):
                 cleaned_config[_k] = flat_add(cleaned_config[_k], _v)
 
             # fetch sources and parse them
-            for src in to_l(d['source']):
-                i += 1
+            if 'source' in d:
+                for src in to_l(d['source']):
+                    i += 1
 
-                # we download the file
-                module_name = os.path.basename(src)
-                if 'http' in src:
-                    path = download_directory
-                    name = 'autocmake_{0}'.format(module_name)
-                    dst = os.path.join(download_directory, 'autocmake_{0}'.format(module_name))
-                    fetch_url(src, dst)
-                    file_name = dst
-                    fetch_dst_directory = download_directory
-                else:
-                    if os.path.exists(src):
-                        path = os.path.dirname(src)
-                        name = module_name
-                        file_name = src
-                        fetch_dst_directory = path
+                    # we download the file
+                    module_name = os.path.basename(src)
+                    if 'http' in src:
+                        path = download_directory
+                        name = 'autocmake_{0}'.format(module_name)
+                        dst = os.path.join(download_directory, 'autocmake_{0}'.format(module_name))
+                        fetch_url(src, dst)
+                        file_name = dst
+                        fetch_dst_directory = download_directory
                     else:
-                        sys.stderr.write("ERROR: {0} does not exist\n".format(src))
-                        sys.exit(-1)
+                        if os.path.exists(src):
+                            path = os.path.dirname(src)
+                            name = module_name
+                            file_name = src
+                            fetch_dst_directory = path
+                        else:
+                            sys.stderr.write("ERROR: {0} does not exist\n".format(src))
+                            sys.exit(-1)
 
-                # we infer config from the module documentation
-                # dictionary d overrides the configuration in the module documentation
-                # this allows to override interpolation inside the module
-                with open(file_name, 'r') as f:
-                    parsed_config = parse_cmake_module(f.read(), d)
-                    for _k2, _v2 in parsed_config.items():
-                        if _k2 not in to_d(v):
-                            # we add to clean_config only if the entry does not exist
-                            # in parent autocmake.yml already
-                            # this allows to override
-                            cleaned_config[_k2] = flat_add(cleaned_config[_k2], _v2)
+                    # we infer config from the module documentation
+                    # dictionary d overrides the configuration in the module documentation
+                    # this allows to override interpolation inside the module
+                    with open(file_name, 'r') as f:
+                        parsed_config = parse_cmake_module(f.read(), d)
+                        for _k2, _v2 in parsed_config.items():
+                            if _k2 not in to_d(v):
+                                # we add to clean_config only if the entry does not exist
+                                # in parent autocmake.yml already
+                                # this allows to override
+                                cleaned_config[_k2] = flat_add(cleaned_config[_k2], _v2)
 
-                modules.append(Module(path=path, name=name))
-                print_progress_bar(text='- assembling modules:',
-                                   done=i,
-                                   total=num_sources,
-                                   width=30)
+                    modules.append(Module(path=path, name=name))
+                    print_progress_bar(text='- assembling modules:',
+                                       done=i,
+                                       total=num_sources,
+                                       width=30)
 
     print('')