diff --git a/packages/mermaid/src/diagrams/git/gitGraphAst.ts b/packages/mermaid/src/diagrams/git/gitGraphAst.ts
index 53c361e3e..1a40450d9 100644
--- a/packages/mermaid/src/diagrams/git/gitGraphAst.ts
+++ b/packages/mermaid/src/diagrams/git/gitGraphAst.ts
@@ -213,7 +213,7 @@ export const merge = (
     id: customId ? customId : state.records.seq + '-' + getID(),
     message: `merged branch ${otherBranch} into ${state.records.currBranch}`,
     seq: state.records.seq++,
-    parents: [state.records.head == null ? null : state.records.head.id, verifiedBranch],
+    parents: state.records.head == null ? [] : [state.records.head.id, verifiedBranch],
     branch: state.records.currBranch,
     type: commitType.MERGE,
     customType: overrideType,
@@ -317,7 +317,7 @@ export const cherryPick = function (
       id: state.records.seq + '-' + getID(),
       message: `cherry-picked ${sourceCommit?.message} into ${state.records.currBranch}`,
       seq: state.records.seq++,
-      parents: [state.records.head == null ? null : state.records.head.id, sourceCommit.id],
+      parents: state.records.head == null ? [] : [state.records.head.id, sourceCommit.id],
       branch: state.records.currBranch,
       type: commitType.CHERRY_PICK,
       tags: tags
diff --git a/packages/mermaid/src/diagrams/git/gitGraphTypes.ts b/packages/mermaid/src/diagrams/git/gitGraphTypes.ts
index 0e929666f..b473dd874 100644
--- a/packages/mermaid/src/diagrams/git/gitGraphTypes.ts
+++ b/packages/mermaid/src/diagrams/git/gitGraphTypes.ts
@@ -15,7 +15,7 @@ export interface Commit {
   seq: number;
   type: number;
   tags: string[];
-  parents: (string | null)[];
+  parents: string[];
   branch: string;
   customType?: number;
   customId?: boolean;
@@ -109,4 +109,4 @@ export interface GitGraphDB extends DiagramDB {
   getHead: () => Commit | null;
 }
 
-export type DiagramOrientation = 'LR' | 'TB';
+export type DiagramOrientation = 'LR' | 'TB' | 'BT';