diff --git a/types/gm/gm-tests.ts b/types/gm/gm-tests.ts
index e882189034..b15a4c7307 100644
--- a/types/gm/gm-tests.ts
+++ b/types/gm/gm-tests.ts
@@ -370,7 +370,10 @@ gm(src).toBuffer(format, (err, buffer) => {
 const imageMagick = gm.subClass({ imageMagick: true });
 readStream = imageMagick(src)
 	.adjoin()
-	.stream();
+    .stream();
+
+const customGm = gm.subClass({ appPath: '' });
+readStream = customGm(src).stream();
 
 const passStream = imageMagick(readStream).stream();
 
diff --git a/types/gm/index.d.ts b/types/gm/index.d.ts
index bcb1117239..9a338142d2 100644
--- a/types/gm/index.d.ts
+++ b/types/gm/index.d.ts
@@ -15,6 +15,7 @@ declare function m(width: number, height: number, color?: string): m.State;
 
 declare namespace m {
     interface ClassOptions {
+        appPath?: string;
         imageMagick?: boolean;
         nativeAutoOrient?: boolean;
     }