diff --git a/types/gm/gm-tests.ts b/types/gm/gm-tests.ts
index ecc8104ec6..e882189034 100644
--- a/types/gm/gm-tests.ts
+++ b/types/gm/gm-tests.ts
@@ -178,6 +178,7 @@ gm(src)
 	.modulate(b, s, h)
 	.monitor()
 	.monochrome()
+	.montage(src)
 	.morph(src, dest)
 	.morph(src, dest, (err, stdout, stderr, cmd) => {
 	})
diff --git a/types/gm/index.d.ts b/types/gm/index.d.ts
index 15117e6cf9..bcb1117239 100644
--- a/types/gm/index.d.ts
+++ b/types/gm/index.d.ts
@@ -184,6 +184,7 @@ declare namespace m {
         modulate(b: number, s: number, h: number): State;
         monitor(): State;
         monochrome(): State;
+        montage(otherImg: string): State;
         morph(otherImg: string | string[], outName: string, callback?: WriteCallback): State;
         mosaic(): State;
         motionBlur(radius: number, sigma?: number, angle?: number): State;