diff --git a/moment-timezone/moment-timezone.d.ts b/moment-timezone/moment-timezone.d.ts
index 85d5b4707..c1d7e2d23 100644
--- a/moment-timezone/moment-timezone.d.ts
+++ b/moment-timezone/moment-timezone.d.ts
@@ -35,22 +35,10 @@ interface MomentTimezone {
     (date: number, timezone: string): moment.Moment;
     (date: number[], timezone: string): moment.Moment;
     (date: string, timezone: string): moment.Moment;
-    (date: string, format: string, timezone: string): moment.Moment;
-    (date: string, format: string, strict: boolean, timezone: string): moment.Moment;
-    (date: string, format: string, language: string, timezone: string): moment.Moment;
-    (date: string, format: string, language: string, strict: boolean, timezone: string): moment.Moment;
-    (date: string, formats: string[], timezone: string): moment.Moment;
-    (date: string, formats: string[], strict: boolean, timezone: string): moment.Moment;
-    (date: string, formats: string[], language: string, timezone: string): moment.Moment;
-    (date: string, formats: string[], language: string, strict: boolean, timezone: string): moment.Moment;
-    (date: string, specialFormat: () => void, timezone: string): moment.Moment;
-    (date: string, specialFormat: () => void, strict: boolean, timezone: string): moment.Moment;
-    (date: string, specialFormat: () => void, language: string, timezone: string): moment.Moment;
-    (date: string, specialFormat: () => void, language: string, strict: boolean, timezone: string): moment.Moment;
-    (date: string, formatsIncludingSpecial: any[], timezone: string): moment.Moment;
-    (date: string, formatsIncludingSpecial: any[], strict: boolean, timezone: string): moment.Moment;
-    (date: string, formatsIncludingSpecial: any[], language: string, timezone: string): moment.Moment;
-    (date: string, formatsIncludingSpecial: any[], language: string, strict: boolean, timezone: string): moment.Moment;
+    (date: string, format: moment.MomentFormatSpecification, timezone: string): moment.Moment;
+    (date: string, format: moment.MomentFormatSpecification, strict: boolean, timezone: string): moment.Moment;
+    (date: string, format: moment.MomentFormatSpecification, language: string, timezone: string): moment.Moment;
+    (date: string, format: moment.MomentFormatSpecification, language: string, strict: boolean, timezone: string): moment.Moment;
     (date: Date, timezone: string): moment.Moment;
     (date: moment.Moment, timezone: string): moment.Moment;
     (date: Object, timezone: string): moment.Moment;
diff --git a/moment/moment-node.d.ts b/moment/moment-node.d.ts
index 13959bbf8..5199a64a2 100644
--- a/moment/moment-node.d.ts
+++ b/moment/moment-node.d.ts
@@ -571,6 +571,12 @@ declare namespace moment {
         yy: any;
     }
 
+    interface MomentBuiltinFormat {
+        __momentBuiltinFormatBrand: any;
+    }
+
+    type MomentFormatSpecification = string | MomentBuiltinFormat | (string | MomentBuiltinFormat)[];
+
     interface MomentStatic {
         version: string;
         fn: Moment;
@@ -578,14 +584,8 @@ declare namespace moment {
         (): Moment;
         (date: number): Moment;
         (date: number[]): Moment;
-        (date: string, format?: string, strict?: boolean): Moment;
-        (date: string, format?: string, language?: string, strict?: boolean): Moment;
-        (date: string, formats: string[], strict?: boolean): Moment;
-        (date: string, formats: string[], language?: string, strict?: boolean): Moment;
-        (date: string, specialFormat: () => void, strict?: boolean): Moment;
-        (date: string, specialFormat: () => void, language?: string, strict?: boolean): Moment;
-        (date: string, formatsIncludingSpecial: any[], strict?: boolean): Moment;
-        (date: string, formatsIncludingSpecial: any[], language?: string, strict?: boolean): Moment;
+        (date: string, format?: MomentFormatSpecification, strict?: boolean): Moment;
+        (date: string, format?: MomentFormatSpecification, language?: string, strict?: boolean): Moment;
         (date: Date): Moment;
         (date: Moment): Moment;
         (date: Object): Moment;
@@ -675,7 +675,7 @@ declare namespace moment {
         /**
          * Constant used to enable explicit ISO_8601 format parsing.
          */
-        ISO_8601(): void;
+        ISO_8601: MomentBuiltinFormat;
 
         defaultFormat: string;
     }