diff --git a/libguile/ChangeLog b/libguile/ChangeLog
index cce8dbb3b..0d91c6b56 100644
--- a/libguile/ChangeLog
+++ b/libguile/ChangeLog
@@ -1,5 +1,11 @@
 2008-04-10  Andy Wingo  <wingo@pobox.com>
 
+	* struct.c (scm_struct_ref, scm_struct_set_x): "Light" structs
+	have no hidden words (members of the SCM_STRUCT_DATA(x) array
+	accessed with negative indices). In that case, determine the
+	number of fields from the length of the struct layout
+	descriptor. (Most GOOPS instances are light structs.)
+
 	* goops.c (wrap_init): Initialize 'u' slots to 0, not some random
 	SCM value.
 
diff --git a/libguile/struct.c b/libguile/struct.c
index c8d34a4db..2d36303b4 100644
--- a/libguile/struct.c
+++ b/libguile/struct.c
@@ -659,7 +659,11 @@ SCM_DEFINE (scm_struct_ref, "struct-ref", 2, 0, 0,
 
   fields_desc = scm_i_symbol_chars (layout);
   layout_len = scm_i_symbol_length (layout);
-  n_fields = data[scm_struct_i_n_words];
+  if (SCM_STRUCT_VTABLE_FLAGS (handle) & SCM_STRUCTF_LIGHT)
+    /* no extra words */
+    n_fields = layout_len / 2;
+  else
+    n_fields = data[scm_struct_i_n_words];
   
   SCM_ASSERT_RANGE(1, pos, p < n_fields);
 
@@ -736,7 +740,11 @@ SCM_DEFINE (scm_struct_set_x, "struct-set!", 3, 0, 0,
 
   fields_desc = scm_i_symbol_chars (layout);
   layout_len = scm_i_symbol_length (layout);
-  n_fields = data[scm_struct_i_n_words];
+  if (SCM_STRUCT_VTABLE_FLAGS (handle) & SCM_STRUCTF_LIGHT)
+    /* no extra words */
+    n_fields = layout_len / 2;
+  else
+    n_fields = data[scm_struct_i_n_words];
 
   SCM_ASSERT_RANGE (1, pos, p < n_fields);