diff --git a/libguile/hashtab.h b/libguile/hashtab.h
index 8f422b0b5..1705cf744 100644
--- a/libguile/hashtab.h
+++ b/libguile/hashtab.h
@@ -33,6 +33,7 @@
 
 /* Types of weak hash tables.  */
 typedef enum {
+  SCM_WEAK_TABLE_KIND_NONE = 0,
   SCM_WEAK_TABLE_KIND_KEY,
   SCM_WEAK_TABLE_KIND_VALUE,
   SCM_WEAK_TABLE_KIND_BOTH
@@ -51,7 +52,9 @@ typedef enum {
 #define SCM_HASHTABLE_DOUBLY_WEAK_P(x) \
   (SCM_HASHTABLE_FLAGS (x) == SCM_WEAK_TABLE_KIND_BOTH)
 
-#define SCM_HASHTABLE_WEAK_P(x)	   SCM_HASHTABLE_FLAGS (x)
+#define SCM_HASHTABLE_WEAK_P(x)				\
+  (SCM_HASHTABLE_FLAGS (x) != SCM_WEAK_TABLE_KIND_NONE)
+
 #define SCM_HASHTABLE_N_ITEMS(x)   (SCM_HASHTABLE (x)->n_items)
 #define SCM_SET_HASHTABLE_N_ITEMS(x, n)   (SCM_HASHTABLE (x)->n_items = n)
 #define SCM_HASHTABLE_INCREMENT(x) (SCM_HASHTABLE_N_ITEMS(x)++)