diff --git a/lightrag/types.py b/lightrag/types.py
index 9c8e0099..d2670ddc 100644
--- a/lightrag/types.py
+++ b/lightrag/types.py
@@ -1,5 +1,5 @@
 from pydantic import BaseModel
-from typing import List, Dict, Any
+from typing import List, Dict, Any, Optional
 
 
 class GPTKeywordExtractionFormat(BaseModel):
@@ -15,7 +15,7 @@ class KnowledgeGraphNode(BaseModel):
 
 class KnowledgeGraphEdge(BaseModel):
     id: str
-    type: str
+    type: Optional[str]
     source: str  # id of source node
     target: str  # id of target node
     properties: Dict[str, Any]  # anything else goes here
diff --git a/lightrag_webui/src/components/PropertiesView.tsx b/lightrag_webui/src/components/PropertiesView.tsx
index 078420e6..dec80460 100644
--- a/lightrag_webui/src/components/PropertiesView.tsx
+++ b/lightrag_webui/src/components/PropertiesView.tsx
@@ -200,7 +200,7 @@ const EdgePropertiesView = ({ edge }: { edge: EdgeType }) => {
       <label className="text-md pl-1 font-bold tracking-wide text-teal-600">Relationship</label>
       <div className="bg-primary/5 max-h-96 overflow-auto rounded p-1">
         <PropertyRow name={'Id'} value={edge.id} />
-        <PropertyRow name={'Type'} value={edge.type} />
+        {edge.type && <PropertyRow name={'Type'} value={edge.type} />}
         <PropertyRow
           name={'Source'}
           value={edge.sourceNode ? edge.sourceNode.labels.join(', ') : edge.source}
diff --git a/lightrag_webui/src/hooks/useLightragGraph.tsx b/lightrag_webui/src/hooks/useLightragGraph.tsx
index 1f82760f..b9c291bc 100644
--- a/lightrag_webui/src/hooks/useLightragGraph.tsx
+++ b/lightrag_webui/src/hooks/useLightragGraph.tsx
@@ -24,7 +24,7 @@ const validateGraph = (graph: RawGraph) => {
   }
 
   for (const edge of graph.edges) {
-    if (!edge.id || !edge.source || !edge.target || !edge.type || !edge.properties) {
+    if (!edge.id || !edge.source || !edge.target) {
       return false
     }
   }
@@ -88,6 +88,14 @@ const fetchGraph = async (label: string) => {
       if (source !== undefined && source !== undefined) {
         const sourceNode = rawData.nodes[source]
         const targetNode = rawData.nodes[target]
+        if (!sourceNode) {
+          console.error(`Source node ${edge.source} is undefined`)
+          continue
+        }
+        if (!targetNode) {
+          console.error(`Target node ${edge.target} is undefined`)
+          continue
+        }
         sourceNode.degree += 1
         targetNode.degree += 1
       }
@@ -146,7 +154,7 @@ const createSigmaGraph = (rawGraph: RawGraph | null) => {
 
   for (const rawEdge of rawGraph?.edges ?? []) {
     rawEdge.dynamicId = graph.addDirectedEdge(rawEdge.source, rawEdge.target, {
-      label: rawEdge.type
+      label: rawEdge.type || undefined
     })
   }
 
diff --git a/lightrag_webui/src/stores/graph.ts b/lightrag_webui/src/stores/graph.ts
index b78e9bf8..b7c2120c 100644
--- a/lightrag_webui/src/stores/graph.ts
+++ b/lightrag_webui/src/stores/graph.ts
@@ -19,7 +19,7 @@ export type RawEdgeType = {
   id: string
   source: string
   target: string
-  type: string
+  type?: string
   properties: Record<string, any>
 
   dynamicId: string