diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index 1907f2993ad..2da02381a46 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -691,7 +691,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			},
 			registerExternalUriOpener(id: string, opener: vscode.ExternalUriOpener, metadata: vscode.ExternalUriOpenerMetadata) {
 				checkProposedApiEnabled(extension);
-				return extHostUriOpeners.registerUriOpener(extension.identifier, id, opener, metadata);
+				return extHostUriOpeners.registerExternalUriOpener(extension.identifier, id, opener, metadata);
 			},
 			get openEditors() {
 				checkProposedApiEnabled(extension);
diff --git a/src/vs/workbench/api/common/extHostUriOpener.ts b/src/vs/workbench/api/common/extHostUriOpener.ts
index 19b91ae4545..81bbc6f4dfc 100644
--- a/src/vs/workbench/api/common/extHostUriOpener.ts
+++ b/src/vs/workbench/api/common/extHostUriOpener.ts
@@ -5,6 +5,7 @@
 
 import { CancellationToken } from 'vs/base/common/cancellation';
 import { toDisposable } from 'vs/base/common/lifecycle';
+import { Schemas } from 'vs/base/common/network';
 import { URI, UriComponents } from 'vs/base/common/uri';
 import * as modes from 'vs/editor/common/modes';
 import { ExtensionIdentifier } from 'vs/platform/extensions/common/extensions';
@@ -14,6 +15,8 @@ import { ExtHostUriOpenersShape, IMainContext, MainContext, MainThreadUriOpeners
 
 export class ExtHostUriOpeners implements ExtHostUriOpenersShape {
 
+	private static readonly supportedSchemes = new Set<string>([Schemas.http, Schemas.https]);
+
 	private readonly _proxy: MainThreadUriOpenersShape;
 
 	private readonly _openers = new Map<string, vscode.ExternalUriOpener>();
@@ -24,7 +27,7 @@ export class ExtHostUriOpeners implements ExtHostUriOpenersShape {
 		this._proxy = mainContext.getProxy(MainContext.MainThreadUriOpeners);
 	}
 
-	registerUriOpener(
+	registerExternalUriOpener(
 		extensionId: ExtensionIdentifier,
 		id: string,
 		opener: vscode.ExternalUriOpener,
@@ -34,6 +37,11 @@ export class ExtHostUriOpeners implements ExtHostUriOpenersShape {
 			throw new Error(`Opener with id '${id}' already registered`);
 		}
 
+		const invalidScheme = metadata.schemes.find(scheme => !ExtHostUriOpeners.supportedSchemes.has(scheme));
+		if (invalidScheme) {
+			throw new Error(`Scheme '${invalidScheme}' is not supported. Only http and https are currently supported.`);
+		}
+
 		this._openers.set(id, opener);
 		this._proxy.$registerUriOpener(id, metadata.schemes, extensionId, metadata.label);