diff --git a/frontend/scanimage.c b/frontend/scanimage.c
index 9e21fded3..a99507ab4 100644
--- a/frontend/scanimage.c
+++ b/frontend/scanimage.c
@@ -1144,6 +1144,8 @@ process_backend_option (SANE_Handle device, int optnum, const char *optarg)
       return;
     }
   set_option (device, optnum, valuep);
+  if (opt->type == SANE_TYPE_STRING && valuep)
+    free(valuep);
 }
 
 static void