diff --git a/libguile/modules.h b/libguile/modules.h
index 34edb328d..480282527 100644
--- a/libguile/modules.h
+++ b/libguile/modules.h
@@ -1,7 +1,7 @@
 #ifndef SCM_MODULES_H
 #define SCM_MODULES_H
 
-/* Copyright 1998,2000-2003,2006-2008,2011-2012,2018
+/* Copyright 1998,2000-2003,2006-2008,2011-2012,2018,2025
      Free Software Foundation, Inc.
 
    This file is part of Guile.
@@ -23,6 +23,7 @@
 
 
 #include "libguile/gc.h"
+#include "libguile/struct.h"
 
 
 
@@ -48,19 +49,19 @@ SCM_API scm_t_bits scm_module_tag;
 #define scm_module_index_import_obarray 8
 
 #define SCM_MODULE_OBARRAY(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module) [scm_module_index_obarray])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_obarray)
 #define SCM_MODULE_USES(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module) [scm_module_index_uses])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_uses)
 #define SCM_MODULE_BINDER(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module) [scm_module_index_binder])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_binder)
 #define SCM_MODULE_EVAL_CLOSURE(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module)[scm_module_index_eval_closure])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_eval_closure)
 #define SCM_MODULE_TRANSFORMER(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module)[scm_module_index_transformer])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_transformer)
 #define SCM_MODULE_DUPLICATE_HANDLERS(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module)[scm_module_index_duplicate_handlers])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_duplicate_handlers)
 #define SCM_MODULE_IMPORT_OBARRAY(module) \
-  SCM_PACK (SCM_STRUCT_DATA (module)[scm_module_index_import_obarray])
+  SCM_STRUCT_SLOT_REF (module, scm_module_index_import_obarray)
 
 
 
diff --git a/libguile/struct.h b/libguile/struct.h
index f616680bd..459bfbd05 100644
--- a/libguile/struct.h
+++ b/libguile/struct.h
@@ -109,13 +109,73 @@
 
 typedef void (*scm_t_struct_finalize) (SCM obj);
 
-#define SCM_STRUCTP(X)  		(!SCM_IMP(X) && (SCM_TYP3(X) == scm_tc3_struct))
-#define SCM_STRUCT_SLOTS(X) 		(SCM_CELL_OBJECT_LOC(X, 1))
-#define SCM_STRUCT_SLOT_REF(X,I) 	(SCM_STRUCT_SLOTS (X)[(I)])
-#define SCM_STRUCT_SLOT_SET(X,I,V) 	SCM_STRUCT_SLOTS (X)[(I)]=(V)
-#define SCM_STRUCT_DATA(X) 		((scm_t_bits*)SCM_STRUCT_SLOTS (X))
-#define SCM_STRUCT_DATA_REF(X,I) 	(SCM_STRUCT_DATA (X)[(I)])
-#define SCM_STRUCT_DATA_SET(X,I,V) 	SCM_STRUCT_DATA (X)[(I)]=(V)
+union scm_struct_slot
+{
+  SCM scm;
+  scm_t_bits raw;
+};
+
+struct scm_struct
+{
+  scm_t_bits tagged_vtable;
+  union scm_struct_slot slots[];
+};
+
+static inline int
+scm_is_struct (SCM x)
+{
+  return SCM_NIMP (x) && (SCM_TYP3 (x) == scm_tc3_struct);
+}
+
+static inline struct scm_struct *
+scm_to_struct (SCM x)
+{
+  if (!scm_is_struct (x))
+    abort ();
+  return (struct scm_struct *) SCM_UNPACK_POINTER (x);
+}
+
+static inline SCM
+scm_from_struct (struct scm_struct *x)
+{
+  return SCM_PACK_POINTER (x);
+}
+
+static inline struct scm_struct *
+scm_i_struct_vtable (struct scm_struct *x)
+{
+  return (struct scm_struct *) (x->tagged_vtable - scm_tc3_struct);
+}
+
+static inline SCM
+scm_i_struct_ref_scm (struct scm_struct *x, size_t idx)
+{
+  return x->slots[idx].scm;
+}
+
+static inline void
+scm_i_struct_set_scm (struct scm_struct *x, size_t idx, SCM val)
+{
+  x->slots[idx].scm = val;
+}
+
+static inline scm_t_bits
+scm_i_struct_ref_raw (struct scm_struct *x, size_t idx)
+{
+  return x->slots[idx].raw;
+}
+
+static inline void
+scm_i_struct_set_raw (struct scm_struct *x, size_t idx, scm_t_bits val)
+{
+  x->slots[idx].raw = val;
+}
+
+#define SCM_STRUCTP(x)  		(scm_is_struct (x))
+#define SCM_STRUCT_SLOT_REF(x,i) 	(scm_i_struct_ref_scm (scm_to_struct (x), i))
+#define SCM_STRUCT_SLOT_SET(x,i,v) 	(scm_i_struct_set_scm (scm_to_struct (x), i, v))
+#define SCM_STRUCT_DATA_REF(x,i) 	(scm_i_struct_ref_raw (scm_to_struct (x), i))
+#define SCM_STRUCT_DATA_SET(x,i,v) 	(scm_i_struct_set_raw (scm_to_struct (x), i, v))
 
 #define SCM_VALIDATE_STRUCT(pos, v) \
   SCM_MAKE_VALIDATE_MSG (pos, v, STRUCTP, "struct")
@@ -129,7 +189,8 @@ typedef void (*scm_t_struct_finalize) (SCM obj);
 #define SCM_VTABLE_LAYOUT(X)            (SCM_STRUCT_SLOT_REF ((X), scm_vtable_index_layout))
 #define SCM_SET_VTABLE_LAYOUT(X,L)      (SCM_STRUCT_SLOT_SET ((X), scm_vtable_index_layout, L))
 #define SCM_VTABLE_FLAGS(X)             (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags))
-#define SCM_SET_VTABLE_FLAGS(X,F)       (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) |= (F))
+#define SCM_SET_VTABLE_FLAGS(X,F)       (SCM_STRUCT_DATA_SET (X, scm_vtable_index_flags, \
+                                                              SCM_VTABLE_FLAGS (X) | (F)))
 #define SCM_CLEAR_VTABLE_FLAGS(X,F)     (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) &= (~(F)))
 #define SCM_VTABLE_FLAG_IS_SET(X,F)     (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) & (F))
 #define SCM_VTABLE_INSTANCE_FINALIZER(X) ((scm_t_struct_finalize)SCM_STRUCT_DATA_REF (X, scm_vtable_index_instance_finalize))