diff --git a/pdf.c b/pdf.c
index 8aa66d4e65d2e105597b6fd6311b259f00e92ca3..0897ab94fe31cb2a3995a192a32d2e5c21da9e5a 100644
--- a/pdf.c
+++ b/pdf.c
@@ -2785,8 +2785,11 @@ lookup_xref(struct Env *aux, size_t nr, size_t gen)
 			n = H_INDEX_UINT(ss, 0, 1);
 
 			if( nr >= base && nr - base < n && check_null_object(ss->seq->elements[1]->seq->elements[nr-base]))
+			{
+				fprintf(stderr, "XRef in section %ld subsection %ld id %ld is null.\n", i, j, nr-base); //DEBUG
 				/* xref type was invalid during parsing */
 				return NULL;
+			}
 
 			if (nr >= base && nr - base < n)
 				return H_INDEX(XREntry, ss, 1, nr - base);