diff --git a/google-maps-static.el b/google-maps-static.el
index 644408d..89c877a 100644
--- a/google-maps-static.el
+++ b/google-maps-static.el
@@ -328,12 +328,20 @@ PLIST can contains this properties:
                (max (min level google-maps-static-maximum-zoom) google-maps-static-minimum-zoom))
     (apply 'google-maps-static-show plist)))
 
-(defun google-maps-static-zoom-in ()
-  "Zoom a Google map in."
-  (interactive)
-  (unless (plist-member google-maps-static-params :zoom)
-    (error "Current zoom level is unknown, cannot zoom in."))
-  (google-maps-static-zoom (1+ (plist-get google-maps-static-params :zoom))))
+(defun google-maps-static-zoom-in (&optional arg)
+  "Zoom a Google map in.
+If the numeric prefix argument ARG is set, zoom in this much levels."
+  (interactive "p")
+  (let* ((arg (if (> 1 arg) 1 arg))
+         (current (or (plist-get google-maps-static-params :zoom)
+                      google-maps-static-default-zoom))
+         (next (if (and (<= (+ arg current) google-maps-static-maximum-zoom)
+                        (>= (+ arg current) google-maps-static-minimum-zoom))
+                   (+ arg current)
+                 google-maps-static-maximum-zoom)))
+    (setq google-maps-static-params
+          (plist-put google-maps-static-params :zoom next))
+  (google-maps-static-zoom next)))
 
 (defun google-maps-static-zoom-out ()
   "Zoom a Google map out."