diff --git a/backend/epjitsu.c b/backend/epjitsu.c
index 7d987dcda..cce6ed0c4 100644
--- a/backend/epjitsu.c
+++ b/backend/epjitsu.c
@@ -4576,13 +4576,13 @@ destroy(struct scanner *s)
     teardown_buffers(s);
 
     if(s->sane.name){
-      free(s->sane.name);
+      free((void *) s->sane.name);
     }
     if(s->sane.vendor){
-      free(s->sane.vendor);
+      free((void *) s->sane.vendor);
     }
     if(s->sane.model){
-      free(s->sane.model);
+      free((void *) s->sane.model);
     }
   
     free(s);
diff --git a/backend/hp4200.c b/backend/hp4200.c
index a069be6b9..19992d67c 100644
--- a/backend/hp4200.c
+++ b/backend/hp4200.c
@@ -2437,7 +2437,7 @@ sane_exit (void)
 	}
       if (device->dev.name)
 	{
-	  free (device->dev.name);
+	  free ((void *) device->dev.name);
 	}
       free (device);
     }
diff --git a/backend/rts8891.c b/backend/rts8891.c
index bdb401159..50f02f9cd 100644
--- a/backend/rts8891.c
+++ b/backend/rts8891.c
@@ -2233,11 +2233,11 @@ sane_close (SANE_Handle handle)
   if (session->dev->model->gamma != session->val[OPT_GAMMA_VECTOR_B].wa)
     free (session->val[OPT_GAMMA_VECTOR_B].wa);
   free (session->val[OPT_MODE].s);
-  free (session->opt[OPT_RESOLUTION].constraint.word_list);
+  free ((void *) session->opt[OPT_RESOLUTION].constraint.word_list);
   for (i = OPT_BUTTON_1; i <= OPT_BUTTON_11; i++)
     {
-      free (session->opt[i].name);
-      free (session->opt[i].title);
+      free ((void *) session->opt[i].name);
+      free ((void *) session->opt[i].title);
     }
 
   free (session);
diff --git a/backend/umax_pp.c b/backend/umax_pp.c
index 90cd4866b..a0ec1ce60 100644
--- a/backend/umax_pp.c
+++ b/backend/umax_pp.c
@@ -1001,9 +1001,9 @@ sane_exit (void)
   for (i = 0; i < num_devices; i++)
     {
       free (devlist[i].port);
-      free (devlist[i].sane.name);
-      free (devlist[i].sane.model);
-      free (devlist[i].sane.vendor);
+      free ((void *) devlist[i].sane.name);
+      free ((void *) devlist[i].sane.model);
+      free ((void *) devlist[i].sane.vendor);
     }
 
   if (devlist != NULL)