diff --git a/scd/apdu.h b/scd/apdu.h
--- a/scd/apdu.h
+++ b/scd/apdu.h
@@ -98,6 +98,7 @@
 #define APDU_CARD_PRESENT  (2)    /* Card is just present.  */
 #define APDU_CARD_ACTIVE   (4)    /* Card is active.  */
 
+extern npth_mutex_t reader_table_lock;
 
 gpg_error_t apdu_init (void);
 
diff --git a/scd/apdu.c b/scd/apdu.c
--- a/scd/apdu.c
+++ b/scd/apdu.c
@@ -147,7 +147,7 @@
 static struct reader_table_s reader_table[MAX_READER];
 
 #ifdef USE_NPTH
-static npth_mutex_t reader_table_lock;
+npth_mutex_t reader_table_lock;
 #endif
 
 
@@ -1992,8 +1992,6 @@
   dl->idx = 0;
   dl->idx_max = 0;
 
-  npth_mutex_lock (&reader_table_lock);
-
 #ifdef HAVE_LIBUSB
   if (!opt.disable_ccid)
     {
@@ -2001,7 +1999,6 @@
       if (err)
         {
           xfree (dl);
-          npth_mutex_unlock (&reader_table_lock);
           return err;
         }
 
@@ -2011,7 +2008,6 @@
             log_debug ("leave: apdu_open_reader => slot=-1 (no ccid)\n");
 
           xfree (dl);
-          npth_mutex_unlock (&reader_table_lock);
           return gpg_error (GPG_ERR_ENODEV);
         }
     }
@@ -2028,7 +2024,6 @@
           if (pcsc_init () < 0)
             {
               xfree (dl);
-              npth_mutex_unlock (&reader_table_lock);
               return gpg_error (GPG_ERR_NO_SERVICE);
             }
         }
@@ -2044,7 +2039,6 @@
               log_error ("error allocating memory for reader list\n");
               if (pcsc.count == 0)
                 release_pcsc_context ();
-              npth_mutex_unlock (&reader_table_lock);
               xfree (dl);
               return err;
             }
@@ -2057,7 +2051,6 @@
           xfree (p);
           if (pcsc.count == 0)
             release_pcsc_context ();
-          npth_mutex_unlock (&reader_table_lock);
           xfree (dl);
           return iso7816_map_sw (pcsc_error_to_sw (r));
         }
@@ -2094,12 +2087,8 @@
               break;
             }
         }
-
-      pcsc.count++;
     }
 
-  npth_mutex_unlock (&reader_table_lock);
-
   *l_p = dl;
   return 0;
 }
@@ -2123,10 +2112,11 @@
         pcsc.rdrname[i] = NULL;
 
       log_assert (pcsc.count > 0);
-      if (--pcsc.count == 0)
+      if (pcsc.count == 0)
         release_pcsc_context ();
     }
   xfree (dl);
+  npth_mutex_unlock (&reader_table_lock);
 }
 
 
diff --git a/scd/app.c b/scd/app.c
--- a/scd/app.c
+++ b/scd/app.c
@@ -715,9 +715,11 @@
       int new_card = 0;
 
       /* Scan the devices to find new device(s).  */
+      npth_mutex_lock (&reader_table_lock);
       err = apdu_dev_list_start (opt.reader_port, &l);
       if (err)
         {
+          npth_mutex_unlock (&reader_table_lock);
           npth_mutex_unlock (&card_list_lock);
           return err;
         }
@@ -747,11 +749,14 @@
           if (err)
             {
               pincache_put (ctrl, slot, NULL, NULL, NULL, 0);
+              npth_mutex_unlock (&reader_table_lock);
               apdu_close_reader (slot);
+              npth_mutex_lock (&reader_table_lock);
             }
         }
 
       apdu_dev_list_finish (l);
+      npth_mutex_unlock (&reader_table_lock);
 
       /* If new device(s), kick the scdaemon loop.  */
       if (new_card)