diff --git a/src/document/html/internal.h b/src/document/html/internal.h
index 85d3a2b1..6c2eede1 100644
--- a/src/document/html/internal.h
+++ b/src/document/html/internal.h
@@ -10,6 +10,7 @@
extern "C" {
#endif
+struct document;
struct document_options;
struct uri;
@@ -43,6 +44,7 @@ enum html_whitespace_state {
struct html_context {
#ifdef CONFIG_CSS
#ifdef CONFIG_LIBCSS
+ struct document *document;
#else
/* The default stylesheet is initially merged into it. When parsing CSS
* from