diff --git a/libctf/ChangeLog b/libctf/ChangeLog
index a7a31e70fc1..9e8129a610e 100644
--- a/libctf/ChangeLog
+++ b/libctf/ChangeLog
@@ -1,3 +1,8 @@
+2020-07-22  Nick Alcock  <nick.alcock@oracle.com>
+
+	* ctf-hash.c (ctf_hashtab_insert): Free the key passed in if
+	there is a key-freeing function and the key already exists.
+
 2020-07-22  Nick Alcock  <nick.alcock@oracle.com>
 
 	* ctf-inlines.h: New file.
diff --git a/libctf/ctf-hash.c b/libctf/ctf-hash.c
index 4696fcb2d43..1c37d7515b4 100644
--- a/libctf/ctf-hash.c
+++ b/libctf/ctf-hash.c
@@ -171,15 +171,15 @@ ctf_hashtab_insert (struct htab *htab, void *key, void *value,
       *slot = malloc (sizeof (ctf_helem_t));
       if (!*slot)
 	return NULL;
+      (*slot)->key = key;
     }
   else
     {
       if (key_free)
-	  key_free ((*slot)->key);
+	  key_free (key);
       if (value_free)
 	  value_free ((*slot)->value);
     }
-  (*slot)->key = key;
   (*slot)->value = value;
   return *slot;
 }