diff --git a/libifupdown/interface-file.c b/libifupdown/interface-file.c
index 0e1d5c4..c9ed2fc 100644
--- a/libifupdown/interface-file.c
+++ b/libifupdown/interface-file.c
@@ -338,14 +338,6 @@ handle_source(struct lif_interface_file_parse_state *state, char *token, char *b
 		return true;
 	}
 
-	if (!strcmp(state->cur_filename, source_filename))
-	{
-		report_error(state, "attempt to source %s would create infinite loop",
-			     source_filename);
-		/* Broken but not fatal */
-		return true;
-	}
-
 	return lif_interface_file_parse(state, source_filename);
 }
 
@@ -395,6 +387,13 @@ keyword_cmp(const void *a, const void *b)
 bool
 lif_interface_file_parse(struct lif_interface_file_parse_state *state, const char *filename)
 {
+	struct lif_dict_entry *entry = lif_dict_find(&state->loaded, filename);
+	if (entry != NULL)
+	{
+		report_error(state, "skipping already included file %s", filename);
+		return true;
+	}
+
 	FILE *f = fopen(filename, "r");
 	if (f == NULL)
 		return false;
@@ -405,6 +404,8 @@ lif_interface_file_parse(struct lif_interface_file_parse_state *state, const cha
 	size_t old_lineno = state->cur_lineno;
 	state->cur_lineno = 0;
 
+	lif_dict_add(&state->loaded, filename, NULL);
+
 	char linebuf[4096];
 	while (lif_fgetline(linebuf, sizeof linebuf, f) != NULL)
 	{
diff --git a/libifupdown/interface-file.h b/libifupdown/interface-file.h
index a15838f..91fae97 100644
--- a/libifupdown/interface-file.h
+++ b/libifupdown/interface-file.h
@@ -23,9 +23,10 @@
 struct lif_interface_file_parse_state {
 	struct lif_interface *cur_iface;
 	struct lif_dict *collection;
-	struct lif_dict *loaded;
 	const char *cur_filename;
 	size_t cur_lineno;
+
+	struct lif_dict loaded;
 };
 
 extern bool lif_interface_file_parse(struct lif_interface_file_parse_state *state, const char *filename);