diff --git a/icons/icons.svg b/icons/icons.svg
index b7ee99f..2cc9f22 100644
--- a/icons/icons.svg
+++ b/icons/icons.svg
@@ -148,8 +148,8 @@
      showgrid="true"
      inkscape:document-units="px"
      inkscape:current-layer="layer1"
-     inkscape:cy="134.56631"
-     inkscape:cx="310.63103"
+     inkscape:cy="141.63738"
+     inkscape:cx="360.12851"
      inkscape:zoom="11.313708"
      inkscape:pageshadow="2"
      inkscape:pageopacity="0.0"
@@ -543,6 +543,16 @@
      inkscape:label="main"
      id="layer1"
      style="display:inline">
+    <path
+       style="opacity:1;fill:none;fill-opacity:1;stroke:#cccccc;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
+       d="m 289.5,451.5 6,-2 6,2 z"
+       id="path6939"
+       inkscape:connector-curvature="0" />
+    <path
+       inkscape:connector-curvature="0"
+       id="path6941"
+       d="m 305.5,451.5 6,-2 6,2 z"
+       style="opacity:1;fill:none;fill-opacity:1;stroke:#cccccc;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1" />
     <path
        style="opacity:1;fill:#000000;fill-opacity:1;stroke:#cccccc;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
        d="m 227.5,425.5 1,5"
@@ -14888,16 +14898,6 @@
       <title
          id="title6917">pergola</title>
     </path>
-    <path
-       style="opacity:1;fill:none;fill-opacity:1;stroke:#000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
-       d="m 289.5,451.5 6,-2 6,2 z"
-       id="path6939"
-       inkscape:connector-curvature="0" />
-    <path
-       inkscape:connector-curvature="0"
-       id="path6941"
-       d="m 305.5,451.5 6,-2 6,2 z"
-       style="opacity:1;fill:none;fill-opacity:1;stroke:#000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1" />
     <path
        style="opacity:1;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
        d="m 311.51172,465 c -0.0577,-0.001 -0.11517,0.007 -0.16992,0.0254 l -6,2 c -0.20422,0.0681 -0.34191,0.25932 -0.3418,0.47461 -2.1e-4,0.008 -2.1e-4,0.0169 0,0.0254 l 0,1.47461 1,0 0,-1 11,0 0,1 1,0 0,-1.46484 c 0.016,-0.22808 -0.12472,-0.43797 -0.3418,-0.50977 l -6,-2 c -0.0473,-0.0157 -0.0967,-0.0243 -0.14648,-0.0254 z"
diff --git a/roentgen/icon.py b/roentgen/icon.py
index a3dc92e..54aedbc 100644
--- a/roentgen/icon.py
+++ b/roentgen/icon.py
@@ -82,6 +82,17 @@ class Icon:
         svg.add(path)
 
 
+def is_standard(id_: str):
+    """ Check whether SVG object ID is standard Inkscape ID. """
+    if id_ == "base":
+        return True
+    for prefix in ["path", "circle", "rect", "defs", "use", "metadata"]:
+        matcher = re.match(prefix + "\\d+", id_)
+        if matcher:
+            return True
+    return False
+
+
 class IconExtractor:
     """
     Extract icons from SVG file.
@@ -116,9 +127,14 @@ class IconExtractor:
                     self.parse(sub_node)
             return
 
-        if (node.hasAttribute("id") and node.hasAttribute("d") and
-                node.getAttribute("id")):
+        if not node.hasAttribute("id") or not node.getAttribute("id"):
+            return
 
+        id_: str = node.getAttribute("id")
+        if is_standard(id_):
+            return
+
+        if node.hasAttribute("d"):
             path: str = node.getAttribute("d")
             matcher = re.match("[Mm] ([0-9.e-]*)[, ]([0-9.e-]*)", path)
             if not matcher:
@@ -139,10 +155,11 @@ class IconExtractor:
                     name = child_node.childNodes[0].nodeValue
                     break
 
-            id_: str = node.getAttribute("id")
             matcher = re.match(STANDARD_INKSCAPE_ID, id_)
             if not matcher:
                 self.icons[id_] = Icon(path, point, id_, name)
+        else:
+            ui.error(f"not standard ID {id_}")
 
     def get_path(self, id_: str) -> (Icon, bool):
         """