diff --git a/extensions/git/src/api/api1.ts b/extensions/git/src/api/api1.ts
index e77f0f2d381..ea233a4672d 100644
--- a/extensions/git/src/api/api1.ts
+++ b/extensions/git/src/api/api1.ts
@@ -189,7 +189,7 @@ export class ApiRepository implements Repository {
 		return this.repository.getRefs(query, cancellationToken);
 	}
 
-	getMergeBase(ref1: string, ref2: string): Promise<string> {
+	getMergeBase(ref1: string, ref2: string): Promise<string | undefined> {
 		return this.repository.getMergeBase(ref1, ref2);
 	}
 
diff --git a/extensions/git/src/api/git.d.ts b/extensions/git/src/api/git.d.ts
index 93854b09124..9748cacbc84 100644
--- a/extensions/git/src/api/git.d.ts
+++ b/extensions/git/src/api/git.d.ts
@@ -233,7 +233,7 @@ export interface Repository {
 
 	getRefs(query: RefQuery, cancellationToken?: CancellationToken): Promise<Ref[]>;
 
-	getMergeBase(ref1: string, ref2: string): Promise<string>;
+	getMergeBase(ref1: string, ref2: string): Promise<string | undefined>;
 
 	tag(name: string, upstream: string): Promise<void>;
 	deleteTag(name: string): Promise<void>;
diff --git a/extensions/git/src/git.ts b/extensions/git/src/git.ts
index 11dfa579d6b..554e4ad8ac8 100644
--- a/extensions/git/src/git.ts
+++ b/extensions/git/src/git.ts
@@ -1434,11 +1434,16 @@ export class Repository {
 		return result;
 	}
 
-	async getMergeBase(ref1: string, ref2: string): Promise<string> {
-		const args = ['merge-base', ref1, ref2];
-		const result = await this.exec(args);
+	async getMergeBase(ref1: string, ref2: string): Promise<string | undefined> {
+		try {
+			const args = ['merge-base', ref1, ref2];
+			const result = await this.exec(args);
 
-		return result.stdout.trim();
+			return result.stdout.trim();
+		}
+		catch (err) {
+			return undefined;
+		}
 	}
 
 	async hashObject(data: string): Promise<string> {
diff --git a/extensions/git/src/historyProvider.ts b/extensions/git/src/historyProvider.ts
index 17dba102718..06fcf917b06 100644
--- a/extensions/git/src/historyProvider.ts
+++ b/extensions/git/src/historyProvider.ts
@@ -175,7 +175,7 @@ export class GitHistoryProvider implements SourceControlHistoryProvider, FileDec
 
 	async resolveHistoryItemGroupCommonAncestor(refId1: string, refId2: string): Promise<{ id: string; ahead: number; behind: number } | undefined> {
 		const ancestor = await this.repository.getMergeBase(refId1, refId2);
-		if (ancestor === '') {
+		if (!ancestor) {
 			return undefined;
 		}
 
diff --git a/extensions/git/src/repository.ts b/extensions/git/src/repository.ts
index 9e32d37f147..eb702dd665e 100644
--- a/extensions/git/src/repository.ts
+++ b/extensions/git/src/repository.ts
@@ -1189,7 +1189,7 @@ export class Repository implements Disposable {
 		return this.run(Operation.Diff, () => this.repository.diffBetweenShortStat(ref1, ref2));
 	}
 
-	getMergeBase(ref1: string, ref2: string): Promise<string> {
+	getMergeBase(ref1: string, ref2: string): Promise<string | undefined> {
 		return this.run(Operation.MergeBase, () => this.repository.getMergeBase(ref1, ref2));
 	}