diff --git a/src/vs/workbench/api/browser/viewsExtensionPoint.ts b/src/vs/workbench/api/browser/viewsExtensionPoint.ts
index fda5c018445..fbeeb50326f 100644
--- a/src/vs/workbench/api/browser/viewsExtensionPoint.ts
+++ b/src/vs/workbench/api/browser/viewsExtensionPoint.ts
@@ -406,7 +406,7 @@ class ViewsExtensionHandler implements IWorkbenchContribution {
 				}
 
 				if (entry.key === 'remote' && !isProposedApiEnabled(extension.description, 'contribViewsRemote')) {
-					collector.warn(localize('ViewContainerRequiresProposedAPI', "View container '{0}' requires 'enableProposedApi' turned on to be added to 'Remote'.", entry.key));
+					collector.warn(localize('ViewContainerRequiresProposedAPI', "View container '{0}' requires 'enabledApiProposals: [\"contribViewsRemote\"]' to be added to 'Remote'.", entry.key));
 					return;
 				}
 
diff --git a/src/vs/workbench/api/common/menusExtensionPoint.ts b/src/vs/workbench/api/common/menusExtensionPoint.ts
index 36a97b077cb..6f7fb8389ca 100644
--- a/src/vs/workbench/api/common/menusExtensionPoint.ts
+++ b/src/vs/workbench/api/common/menusExtensionPoint.ts
@@ -750,7 +750,7 @@ menusExtensionPoint.setHandler(extensions => {
 			}
 
 			if (menu.proposed && !isProposedApiEnabled(extension.description, menu.proposed)) {
-				collector.error(localize('proposedAPI.invalid', "{0} is a proposed menu identifier and is only available when running out of dev or with the following command line switch: --enable-proposed-api {1}", entry.key, extension.description.identifier.value));
+				collector.error(localize('proposedAPI.invalid', "{0} is a proposed menu identifier. It requires 'package.json#enabledApiProposals: [\"{1}\"]' and is only available when running out of dev or with the following command line switch: --enable-proposed-api {2}", entry.key, menu.proposed, extension.description.identifier.value));
 				return;
 			}
 
diff --git a/src/vs/workbench/contrib/welcome/common/viewsWelcomeContribution.ts b/src/vs/workbench/contrib/welcome/common/viewsWelcomeContribution.ts
index adc14db0b19..91f6b79e2e5 100644
--- a/src/vs/workbench/contrib/welcome/common/viewsWelcomeContribution.ts
+++ b/src/vs/workbench/contrib/welcome/common/viewsWelcomeContribution.ts
@@ -74,7 +74,7 @@ function parseGroupAndOrder(welcome: ViewWelcome, contribution: IExtensionPointU
 	let order: number | undefined;
 	if (welcome.group) {
 		if (!isProposedApiEnabled(contribution.description, 'contribViewsWelcome')) {
-			contribution.collector.warn(nls.localize('ViewsWelcomeExtensionPoint.proposedAPI', "The viewsWelcome contribution in '{0}' requires 'enableProposedApi' to be enabled, in order to use the 'group' proposed property.", contribution.description.identifier.value));
+			contribution.collector.warn(nls.localize('ViewsWelcomeExtensionPoint.proposedAPI', "The viewsWelcome contribution in '{0}' requires 'enabledApiProposals: [\"contribViewsWelcome\"]' in order to use the 'group' proposed property.", contribution.description.identifier.value));
 			return { group, order };
 		}
 
diff --git a/src/vs/workbench/services/extensions/common/extensions.ts b/src/vs/workbench/services/extensions/common/extensions.ts
index 3ef6cdd288e..5eccd39dc01 100644
--- a/src/vs/workbench/services/extensions/common/extensions.ts
+++ b/src/vs/workbench/services/extensions/common/extensions.ts
@@ -143,7 +143,7 @@ export function isProposedApiEnabled(extension: IExtensionDescription, proposal:
 
 export function checkProposedApiEnabled(extension: IExtensionDescription, proposal: ApiProposalName): void {
 	if (!isProposedApiEnabled(extension, proposal)) {
-		throw new Error(`[${extension.identifier.value}]: Proposed API is only available when running out of dev or with the following command line switch: --enable-proposed-api ${extension.identifier.value}`);
+		throw new Error(`Extension '${extension.identifier.value}' CANNOT use API proposal: ${proposal}.\nAccording to its package.json#enabledApiProposals-property it wants: ${extension.enabledApiProposals?.join(', ') ?? '<none>'}.\n You MUST start in extension development mode or use the following command line switch: --enable-proposed-api ${extension.identifier.value}`);
 	}
 }
 
diff --git a/src/vs/workbench/services/themes/common/iconExtensionPoint.ts b/src/vs/workbench/services/themes/common/iconExtensionPoint.ts
index 67bd0f3f868..b7d60683e0b 100644
--- a/src/vs/workbench/services/themes/common/iconExtensionPoint.ts
+++ b/src/vs/workbench/services/themes/common/iconExtensionPoint.ts
@@ -127,7 +127,7 @@ export class IconExtensionPoint {
 				const collector = extension.collector;
 
 				if (!isProposedApiEnabled(extension.description, 'contribIcons')) {
-					collector.error(nls.localize('invalid.icons.proposedAPI', "'configuration.icons is a proposed contribution point and only available when running out of dev or with the following command line switch: --enable-proposed-api {0}", extension.description.identifier.value));
+					collector.error(nls.localize('invalid.icons.proposedAPI', "'configuration.icons is a proposed contribution point. It requires 'package.json#enabledApiProposals: [\"contribIcons\"]' and is only available when running out of dev or with the following command line switch: --enable-proposed-api {0}", extension.description.identifier.value));
 					return;
 				}
 
@@ -181,7 +181,7 @@ export class IconFontExtensionPoint {
 				const collector = extension.collector;
 
 				if (!isProposedApiEnabled(extension.description, 'contribIconFonts')) {
-					collector.error(nls.localize('invalid.iconFonts.proposedAPI', "'configuration.iconFonts is a proposed contribution point and only available when running out of dev or with the following command line switch: --enable-proposed-api {0}", extension.description.identifier.value));
+					collector.error(nls.localize('invalid.iconFonts.proposedAPI', "'configuration.iconFonts is a proposed contribution point. It requires 'package.json#enabledApiProposals: [\"contribIconFonts\"]' and is and only available when running out of dev or with the following command line switch: --enable-proposed-api {0}", extension.description.identifier.value));
 					return;
 				}