diff --git a/index.d.ts b/index.d.ts
index d3531b51..121ec2f6 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -96,7 +96,16 @@ declare namespace JSZip {
          * The last modification date, defaults to the current date.
          */
         date?: Date;
-        compression?: string;
+        /**
+         * Sets per file compression. The `compressionOptions` parameter depends on the compression type.
+         */
+        compression?: Compression;
+        /**
+         * Sets per file compression level. With `STORE` (no compression), this parameter is ignored. With `DEFLATE`, you can give the compression level with `compressionOptions : {level:6}` (or any level between 1 (best speed) and 9 (best compression)).
+         */
+        compressionOptions?: null | {
+            level: number;
+        };
         comment?: string;
         /** Set to `true` if (and only if) the input is a "binary string" and has already been prepared with a `0xFF` mask. */
         optimizedBinaryString?: boolean;
@@ -119,7 +128,13 @@ declare namespace JSZip {
     }
 
     interface JSZipGeneratorOptions<T extends OutputType = OutputType> {
+        /**
+         * Sets compression option for all entries that have not specified their own `compression` option
+         */
         compression?: Compression;
+        /**
+         * The `compressionOptions` parameter depends on the compression type. With `STORE` (no compression), this parameter is ignored. With `DEFLATE`, you can give the compression level with `compressionOptions : {level:6}` (or any level between 1 (best speed) and 9 (best compression)).
+         */
         compressionOptions?: null | {
             level: number;
         };