diff --git a/src/main/ua-parser.d.ts b/src/main/ua-parser.d.ts
index 2d6f9b6..3fa5749 100644
--- a/src/main/ua-parser.d.ts
+++ b/src/main/ua-parser.d.ts
@@ -48,7 +48,7 @@ declare namespace UAParser {
 
     type RegexMap = ((RegExp | string | (string | RegExp | Function)[])[])[];
     type UAParserProps = 'browser' | 'cpu' | 'device' | 'engine' | 'os';
-    type UAParserExt = Record<UAParserProps, RegexMap>;
+    type UAParserExt = Partial<Record<UAParserProps, RegexMap>>;
 
     export function UAParser(uastring?: string, extensions?: UAParserExt, headers?: Record<string, string>): IResult;
     export function UAParser(uastring?: string, headers?: Record<string, string>): IResult;