diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 0d92cbe6531ef..cb43388b2dd00 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18613,7 +18613,7 @@ namespace ts {
                 case SyntaxKind.ParenthesizedExpression: {
                     // Like in `checkParenthesizedExpression`, an `/** @type {xyz} */` comment before a parenthesized expression acts as a type cast.
                     const tag = isInJSFile(parent) ? getJSDocTypeTag(parent) : undefined;
-                    return tag ? getTypeFromTypeNode(tag.typeExpression!.type) : getContextualType(<ParenthesizedExpression>parent, contextFlags);
+                    return tag ? getTypeFromTypeNode(tag.typeExpression.type) : getContextualType(<ParenthesizedExpression>parent, contextFlags);
                 }
                 case SyntaxKind.JsxExpression:
                     return getContextualTypeForJsxExpression(<JsxExpression>parent);
@@ -24231,7 +24231,7 @@ namespace ts {
         function checkParenthesizedExpression(node: ParenthesizedExpression, checkMode?: CheckMode): Type {
             const tag = isInJSFile(node) ? getJSDocTypeTag(node) : undefined;
             if (tag) {
-                return checkAssertionWorker(tag, tag.typeExpression!.type, node.expression, checkMode);
+                return checkAssertionWorker(tag, tag.typeExpression.type, node.expression, checkMode);
             }
             return checkExpression(node.expression, checkMode);
         }
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 3742f2d5fdf11..f562a6b5d12be 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -2189,7 +2189,7 @@ namespace ts {
     }
 
     /* @internal */
-    export function createJSDocTypeTag(typeExpression?: JSDocTypeExpression, comment?: string): JSDocTypeTag {
+    export function createJSDocTypeTag(typeExpression: JSDocTypeExpression, comment?: string): JSDocTypeTag {
         const tag = createJSDocTag<JSDocTypeTag>(SyntaxKind.JSDocTypeTag, "type");
         tag.typeExpression = typeExpression;
         tag.comment = comment;
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 0d130c6de6506..a86dba52c87af 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -6855,7 +6855,7 @@ namespace ts {
                 }
 
                 function parseReturnTag(start: number, tagName: Identifier): JSDocReturnTag {
-                    if (forEach(tags, t => t.kind === SyntaxKind.JSDocReturnTag)) {
+                    if (some(tags, isJSDocReturnTag)) {
                         parseErrorAt(tagName.pos, scanner.getTokenPos(), Diagnostics._0_tag_already_specified, tagName.escapedText);
                     }
 
@@ -6866,7 +6866,7 @@ namespace ts {
                 }
 
                 function parseTypeTag(start: number, tagName: Identifier): JSDocTypeTag {
-                    if (forEach(tags, t => t.kind === SyntaxKind.JSDocTypeTag)) {
+                    if (some(tags, isJSDocTypeTag)) {
                         parseErrorAt(tagName.pos, scanner.getTokenPos(), Diagnostics._0_tag_already_specified, tagName.escapedText);
                     }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index e141e2b9daa82..5e2d6aba474ee 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2482,7 +2482,7 @@ namespace ts {
 
     export interface JSDocTypeTag extends JSDocTag {
         kind: SyntaxKind.JSDocTypeTag;
-        typeExpression?: JSDocTypeExpression;
+        typeExpression: JSDocTypeExpression;
     }
 
     export interface JSDocTypedefTag extends JSDocTag, NamedDeclaration {
diff --git a/src/services/jsDoc.ts b/src/services/jsDoc.ts
index 8016b0e9ff655..f14a3a1e5d528 100644
--- a/src/services/jsDoc.ts
+++ b/src/services/jsDoc.ts
@@ -134,7 +134,7 @@ namespace ts.JsDoc {
             case SyntaxKind.JSDocTemplateTag:
                 return withList((tag as JSDocTemplateTag).typeParameters);
             case SyntaxKind.JSDocTypeTag:
-                return withNode((tag as JSDocTypeTag).typeExpression!);
+                return withNode((tag as JSDocTypeTag).typeExpression);
             case SyntaxKind.JSDocTypedefTag:
             case SyntaxKind.JSDocCallbackTag:
             case SyntaxKind.JSDocPropertyTag:
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index d09582078be43..fb95102e79126 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -1603,7 +1603,7 @@ declare namespace ts {
     }
     interface JSDocTypeTag extends JSDocTag {
         kind: SyntaxKind.JSDocTypeTag;
-        typeExpression?: JSDocTypeExpression;
+        typeExpression: JSDocTypeExpression;
     }
     interface JSDocTypedefTag extends JSDocTag, NamedDeclaration {
         parent: JSDoc;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 817276dc5c5c6..170cb00b9e879 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -1603,7 +1603,7 @@ declare namespace ts {
     }
     interface JSDocTypeTag extends JSDocTag {
         kind: SyntaxKind.JSDocTypeTag;
-        typeExpression?: JSDocTypeExpression;
+        typeExpression: JSDocTypeExpression;
     }
     interface JSDocTypedefTag extends JSDocTag, NamedDeclaration {
         parent: JSDoc;