diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 71c72a4cf82..e3494a1f341 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -33314,7 +33314,8 @@ namespace ts {
 
                 // Modifiers are never allowed on properties except for 'async' on a method declaration
                 if (prop.modifiers) {
-                    for (const mod of prop.modifiers) {
+                    // eslint-disable-next-line no-unnecessary-type-assertion
+                    for (const mod of prop.modifiers!) { // TODO: GH#19955
                         if (mod.kind !== SyntaxKind.AsyncKeyword || prop.kind !== SyntaxKind.MethodDeclaration) {
                             grammarErrorOnNode(mod, Diagnostics._0_modifier_cannot_be_used_here, getTextOfNode(mod));
                         }