diff --git a/src/parse/index.ts b/src/parse/index.ts
index c81d2f61b0..91d7c3253d 100644
--- a/src/parse/index.ts
+++ b/src/parse/index.ts
@@ -112,14 +112,14 @@ export class Parser {
 		throw new ParseError(message, this.template, index, this.filename);
 	}
 
-	eat(str: string, required?: boolean) {
+	eat(str: string, required?: boolean, message?: string) {
 		if (this.match(str)) {
 			this.index += str.length;
 			return true;
 		}
 
 		if (required) {
-			this.error(`Expected ${str}`);
+			this.error(message || `Expected ${str}`);
 		}
 
 		return false;
diff --git a/src/parse/state/mustache.ts b/src/parse/state/mustache.ts
index bd1db07460..0a255b1256 100644
--- a/src/parse/state/mustache.ts
+++ b/src/parse/state/mustache.ts
@@ -6,7 +6,7 @@ import { Parser } from '../index';
 import { Node } from '../../interfaces';
 
 function trimWhitespace(block: Node, trimBefore: boolean, trimAfter: boolean) {
-	if (!block.children) return; // AwaitBlock
+	if (!block.children || block.children.length === 0) return; // AwaitBlock
 
 	const firstChild = block.children[0];
 	const lastChild = block.children[block.children.length - 1];
@@ -74,8 +74,6 @@ export default function mustache(parser: Parser) {
 		}
 
 		// strip leading/trailing whitespace as necessary
-		if (block.children && !block.children.length) parser.error(`Empty block`, block.start);
-
 		const charBefore = parser.template[block.start - 1];
 		const charAfter = parser.template[parser.index];
 		const trimBefore = !charBefore || whitespace.test(charBefore);
diff --git a/src/parse/state/tag.ts b/src/parse/state/tag.ts
index 8b701cae1d..57e2b1bbb9 100644
--- a/src/parse/state/tag.ts
+++ b/src/parse/state/tag.ts
@@ -71,7 +71,7 @@ export default function tag(parser: Parser) {
 
 	if (parser.eat('!--')) {
 		const data = parser.readUntil(/-->/);
-		parser.eat('-->');
+		parser.eat('-->', true, 'comment was left open, expected -->');
 
 		parser.current().children.push({
 			start,
diff --git a/src/validate/html/index.ts b/src/validate/html/index.ts
index b2a190696f..9ae50baca1 100644
--- a/src/validate/html/index.ts
+++ b/src/validate/html/index.ts
@@ -12,6 +12,13 @@ const meta = new Map([
 	[':Head', validateHead]
 ]);
 
+function isEmptyBlock(node: Node) {
+	if (!/Block$/.test(node.type) || !node.children) return false;
+	if (node.children.length > 1) return false;
+	const child = node.children[0];
+	return !child || (child.type === 'Text' && !/\S/.test(child.data));
+}
+
 export default function validateHtml(validator: Validator, html: Node) {
 	const refs = new Map();
 	const refCallees: Node[] = [];
@@ -58,6 +65,10 @@ export default function validateHtml(validator: Validator, html: Node) {
 			}
 		}
 
+		if (validator.options.dev && isEmptyBlock(node)) {
+			validator.warn('Empty block', node.start);
+		}
+
 		if (node.children) {
 			if (node.type === 'Element') elementStack.push(node);
 			stack.push(node);
diff --git a/src/validate/index.ts b/src/validate/index.ts
index b57f2b0c2a..da603a437b 100644
--- a/src/validate/index.ts
+++ b/src/validate/index.ts
@@ -93,7 +93,7 @@ export default function validate(
 	stylesheet: Stylesheet,
 	options: CompileOptions
 ) {
-	const { onwarn, onerror, name, filename, store } = options;
+	const { onwarn, onerror, name, filename, store, dev } = options;
 
 	try {
 		if (name && !/^[a-zA-Z_$][a-zA-Z_$0-9]*$/.test(name)) {
@@ -114,7 +114,8 @@ export default function validate(
 			onwarn,
 			name,
 			filename,
-			store
+			store,
+			dev
 		});
 
 		if (parsed.js) {
diff --git a/test/parser/samples/error-comment-unclosed/error.json b/test/parser/samples/error-comment-unclosed/error.json
new file mode 100644
index 0000000000..f392e12fa1
--- /dev/null
+++ b/test/parser/samples/error-comment-unclosed/error.json
@@ -0,0 +1,8 @@
+{
+	"message": "comment was left open, expected -->",
+	"loc": {
+		"line": 1,
+		"column": 24
+	},
+	"pos": 24
+}
diff --git a/test/parser/samples/error-comment-unclosed/input.html b/test/parser/samples/error-comment-unclosed/input.html
new file mode 100644
index 0000000000..725cf9be60
--- /dev/null
+++ b/test/parser/samples/error-comment-unclosed/input.html
@@ -0,0 +1 @@
+<!-- an unclosed comment
diff --git a/test/validator/index.js b/test/validator/index.js
index 176d060faf..0a132a7c9e 100644
--- a/test/validator/index.js
+++ b/test/validator/index.js
@@ -1,6 +1,6 @@
 import * as fs from "fs";
 import assert from "assert";
-import { svelte, tryToLoadJson } from "../helpers.js";
+import { svelte, loadConfig, tryToLoadJson } from "../helpers.js";
 
 describe("validate", () => {
 	fs.readdirSync("test/validator/samples").forEach(dir => {
@@ -15,6 +15,7 @@ describe("validate", () => {
 		}
 
 		(solo ? it.only : skip ? it.skip : it)(dir, () => {
+			const config = loadConfig(`./validator/samples/${dir}/_config.js`);
 			const filename = `test/validator/samples/${dir}/input.html`;
 			const input = fs.readFileSync(filename, "utf-8").replace(/\s+$/, "");
 
@@ -32,7 +33,8 @@ describe("validate", () => {
 							pos: warning.pos,
 							loc: warning.loc
 						});
-					}
+					},
+					dev: config.dev
 				});
 
 				assert.deepEqual(warnings, expectedWarnings);
diff --git a/test/validator/samples/each-block-multiple-children/_config.js b/test/validator/samples/each-block-multiple-children/_config.js
new file mode 100644
index 0000000000..e26996239d
--- /dev/null
+++ b/test/validator/samples/each-block-multiple-children/_config.js
@@ -0,0 +1,3 @@
+export default {
+	dev: true
+};
\ No newline at end of file
diff --git a/test/validator/samples/each-block-multiple-children/input.html b/test/validator/samples/each-block-multiple-children/input.html
new file mode 100644
index 0000000000..9d996a3acf
--- /dev/null
+++ b/test/validator/samples/each-block-multiple-children/input.html
@@ -0,0 +1,10 @@
+{{#each things as thing}}
+	<span>this only exists...</span>
+	<span>...to increase test coverage</span>
+{{/each}}
+
+{{#each things as thing}}{{soDoesThis}}{{/each}}
+
+{{#each things as thing}}
+	andThis
+{{/each}}
\ No newline at end of file
diff --git a/test/validator/samples/each-block-multiple-children/warnings.json b/test/validator/samples/each-block-multiple-children/warnings.json
new file mode 100644
index 0000000000..0637a088a0
--- /dev/null
+++ b/test/validator/samples/each-block-multiple-children/warnings.json
@@ -0,0 +1 @@
+[]
\ No newline at end of file
diff --git a/test/validator/samples/empty-block-dev/_config.js b/test/validator/samples/empty-block-dev/_config.js
new file mode 100644
index 0000000000..e26996239d
--- /dev/null
+++ b/test/validator/samples/empty-block-dev/_config.js
@@ -0,0 +1,3 @@
+export default {
+	dev: true
+};
\ No newline at end of file
diff --git a/test/validator/samples/empty-block-dev/input.html b/test/validator/samples/empty-block-dev/input.html
new file mode 100644
index 0000000000..32b892d470
--- /dev/null
+++ b/test/validator/samples/empty-block-dev/input.html
@@ -0,0 +1,5 @@
+{{#each things as thing}}
+
+{{/each}}
+
+{{#each things as thing}}{{/each}}
\ No newline at end of file
diff --git a/test/validator/samples/empty-block-dev/warnings.json b/test/validator/samples/empty-block-dev/warnings.json
new file mode 100644
index 0000000000..54584bf135
--- /dev/null
+++ b/test/validator/samples/empty-block-dev/warnings.json
@@ -0,0 +1,18 @@
+[
+	{
+		"message": "Empty block",
+		"loc": {
+			"line": 1,
+			"column": 0
+		},
+		"pos": 0
+	},
+	{
+		"message": "Empty block",
+		"loc": {
+			"line": 5,
+			"column": 0
+		},
+		"pos": 38
+	}
+]
\ No newline at end of file
diff --git a/test/validator/samples/empty-block-prod/input.html b/test/validator/samples/empty-block-prod/input.html
new file mode 100644
index 0000000000..32b892d470
--- /dev/null
+++ b/test/validator/samples/empty-block-prod/input.html
@@ -0,0 +1,5 @@
+{{#each things as thing}}
+
+{{/each}}
+
+{{#each things as thing}}{{/each}}
\ No newline at end of file
diff --git a/test/validator/samples/empty-block-prod/warnings.json b/test/validator/samples/empty-block-prod/warnings.json
new file mode 100644
index 0000000000..0637a088a0
--- /dev/null
+++ b/test/validator/samples/empty-block-prod/warnings.json
@@ -0,0 +1 @@
+[]
\ No newline at end of file