diff --git a/integration/_payload-limits.json b/integration/_payload-limits.json
index 21cb9fbcb1..54704a01b4 100644
--- a/integration/_payload-limits.json
+++ b/integration/_payload-limits.json
@@ -30,7 +30,7 @@
     "master": {
       "uncompressed": {
         "runtime-es2015": 1485,
-        "main-es2015": 136777,
+        "main-es2015": 137320,
         "polyfills-es2015": 37334
       }
     }
@@ -64,4 +64,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}
diff --git a/packages/core/src/render3/i18n.ts b/packages/core/src/render3/i18n.ts
index 04888681e5..5bcda795a8 100644
--- a/packages/core/src/render3/i18n.ts
+++ b/packages/core/src/render3/i18n.ts
@@ -441,6 +441,15 @@ function i18nStartFirstPass(
       for (let j = 0; j < parts.length; j++) {
         if (j & 1) {
           // Odd indexes are ICU expressions
+          const icuExpression = parts[j] as IcuExpression;
+
+          // Verify that ICU expression has the right shape. Translations might contain invalid
+          // constructions (while original messages were correct), so ICU parsing at runtime may not
+          // succeed (thus `icuExpression` remains a string).
+          if (typeof icuExpression !== 'object') {
+            throw new Error(`Unable to parse ICU expression in "${templateTranslation}" message.`);
+          }
+
           // Create the comment node that will anchor the ICU expression
           const icuNodeIndex = startIndex + i18nVarsCount++;
           createOpCodes.push(
@@ -448,7 +457,6 @@ function i18nStartFirstPass(
               parentIndex << I18nMutateOpCode.SHIFT_PARENT | I18nMutateOpCode.AppendChild);
 
           // Update codes for the ICU expression
-          const icuExpression = parts[j] as IcuExpression;
           const mask = getBindingMask(icuExpression);
           icuStart(icuExpressions, icuExpression, icuNodeIndex, icuNodeIndex);
           // Since this is recursive, the last TIcu that was pushed is the one we want
diff --git a/packages/core/test/acceptance/i18n_spec.ts b/packages/core/test/acceptance/i18n_spec.ts
index 1a45e7cacc..c32c56f02b 100644
--- a/packages/core/test/acceptance/i18n_spec.ts
+++ b/packages/core/test/acceptance/i18n_spec.ts
@@ -2119,6 +2119,55 @@ onlyInIvy('Ivy i18n logic').describe('runtime i18n', () => {
     });
   });
 
+  describe('invalid translations handling', () => {
+    it('should throw in case invalid ICU is present in a template', () => {
+      // Error message is produced by Compiler.
+      expect(() => initWithTemplate(AppComp, '{count, select, 10 {ten} other {other}'))
+          .toThrowError(
+              /Invalid ICU message. Missing '}'. \("{count, select, 10 {ten} other {other}\[ERROR ->\]"\)/);
+    });
+
+    it('should throw in case invalid ICU is present in translation', () => {
+      loadTranslations({
+        [computeMsgId('{VAR_SELECT, select, 10 {ten} other {other}}')]:
+            // Missing "}" at the end of translation.
+            '{VAR_SELECT, select, 10 {dix} other {autre}'
+      });
+
+      // Error message is produced at runtime.
+      expect(() => initWithTemplate(AppComp, '{count, select, 10 {ten} other {other}}'))
+          .toThrowError(
+              /Unable to parse ICU expression in "{�0�, select, 10 {dix} other {autre}" message./);
+    });
+
+    it('should throw in case unescaped curly braces are present in a template', () => {
+      // Error message is produced by Compiler.
+      expect(() => initWithTemplate(AppComp, 'Text { count }'))
+          .toThrowError(
+              /Do you have an unescaped "{" in your template\? Use "{{ '{' }}"\) to escape it/);
+    });
+
+    it('should throw in case curly braces are added into translation', () => {
+      loadTranslations({
+        // Curly braces which were not present in a template were added into translation.
+        [computeMsgId('Text')]: 'Text { count }',
+      });
+      expect(() => initWithTemplate(AppComp, '<div i18n>Text</div>'))
+          .toThrowError(/Unable to parse ICU expression in "Text { count }" message./);
+    });
+  });
+
+  it('should handle extra HTML in translation as plain text', () => {
+    loadTranslations({
+      // Translation contains HTML tags that were not present in original message.
+      [computeMsgId('Text')]: 'Text <div *ngIf="true">Extra content</div>',
+    });
+    const fixture = initWithTemplate(AppComp, '<div i18n>Text</div>');
+
+    const element = fixture.nativeElement;
+    expect(element).toHaveText('Text <div *ngIf="true">Extra content</div>');
+  });
+
   it('should reflect lifecycle hook changes in text interpolations in i18n block', () => {
     @Directive({selector: 'input'})
     class InputsDir {