diff --git a/extensions/git/src/commands.ts b/extensions/git/src/commands.ts
index 0212f1cbec107a913328ecbb0687a119c87f7204..3eaa99748b3c113c3d3b24ce5d04aa29d0f85baf 100644
--- a/extensions/git/src/commands.ts
+++ b/extensions/git/src/commands.ts
@@ -6,7 +6,7 @@
 'use strict';
 
 import { Uri, commands, scm, Disposable, window, workspace, QuickPickItem, OutputChannel, Range, WorkspaceEdit, Position, LineChange, SourceControlResourceState, TextDocumentShowOptions, ViewColumn } from 'vscode';
-import { Ref, RefType, Git, GitErrorCodes } from './git';
+import { Ref, RefType, Git, GitErrorCodes, Branch } from './git';
 import { Model, Resource, Status, CommitOptions, WorkingTreeGroup, IndexGroup, MergeGroup } from './model';
 import { toGitUri, fromGitUri } from './uri';
 import { applyLineChanges, intersectDiffWithRange, toLineRanges, invertLineChange } from './staging';
@@ -85,7 +85,7 @@ class MergeItem implements QuickPickItem {
 	constructor(protected ref: Ref) { }
 
 	async run(model: Model): Promise<void> {
-		await model.merge(this.ref.name);
+		await model.merge(this.ref.name! || this.ref.commit!);
 	}
 }
 
@@ -783,10 +783,12 @@ export class CommandCenter {
 		const includeRemotes = checkoutType === 'all' || checkoutType === 'remote';
 
 		const heads = this.model.refs.filter(ref => ref.type === RefType.Head)
-			.map(ref => new MergeItem(ref));
+			.filter(ref => ref.name || ref.commit)
+			.map(ref => new MergeItem(ref as Branch));
 
 		const remoteHeads = (includeRemotes ? this.model.refs.filter(ref => ref.type === RefType.RemoteHead) : [])
-			.map(ref => new MergeItem(ref));
+			.filter(ref => ref.name || ref.commit)
+			.map(ref => new MergeItem(ref as Branch));
 
 		const picks = [...heads, ...remoteHeads];
 		const placeHolder = localize('select a branch to merge from', 'Select a branch to merge from');
@@ -796,7 +798,16 @@ export class CommandCenter {
 			return;
 		}
 
-		await choice.run(this.model);
+		try {
+			await choice.run(this.model);
+		} catch (err) {
+			if (err.gitErrorCode !== GitErrorCodes.Conflict) {
+				throw err;
+			}
+
+			const message = localize('merge conflicts', "There are merge conflicts. Resolve them before committing.");
+			await window.showWarningMessage(message);
+		}
 	}
 
 	@command('git.pull')
diff --git a/extensions/git/src/git.ts b/extensions/git/src/git.ts
index 865fd06e18d8a47fc4fb27f33c3ca608046e98cc..28e918ef536ac599cfcd73a855015a19c49bfaaf 100644
--- a/extensions/git/src/git.ts
+++ b/extensions/git/src/git.ts
@@ -654,9 +654,18 @@ export class Repository {
 		await this.run(args);
 	}
 
-	async merge(name: string): Promise<void> {
-		const args = ['merge', name];
-		await this.run(args);
+	async merge(ref: string): Promise<void> {
+		const args = ['merge', ref];
+
+		try {
+			await this.run(args);
+		} catch (err) {
+			if (/^CONFLICT /m.test(err.stdout || '')) {
+				err.gitErrorCode = GitErrorCodes.Conflict;
+			}
+
+			throw err;
+		}
 	}
 
 	async clean(paths: string[]): Promise<void> {
diff --git a/extensions/git/src/model.ts b/extensions/git/src/model.ts
index f213b6151c709b7ae2093c3e028f23a547d58197..073cb39fc8fd4c15d28eaa83b8a5e7ce34b42c39 100644
--- a/extensions/git/src/model.ts
+++ b/extensions/git/src/model.ts
@@ -461,8 +461,8 @@ export class Model implements Disposable {
 		await this.run(Operation.DeleteBranch, () => this.repository.deleteBranch(name, force));
 	}
 
-	async merge(name: string): Promise<void> {
-		await this.run(Operation.Merge, () => this.repository.merge(name));
+	async merge(ref: string): Promise<void> {
+		await this.run(Operation.Merge, () => this.repository.merge(ref));
 	}
 
 	async checkout(treeish: string): Promise<void> {