diff --git a/README.md b/README.md
index be66c8ae3..22a6a0b88 100644
--- a/README.md
+++ b/README.md
@@ -162,7 +162,7 @@ If *filter* is specified, sets the filter to the specified function and returns
 
 ```js
 function filter() {
-  return !d3.event.button;
+  return !d3.event.ctrlKey && !d3.event.button;
 }
 ```
 
diff --git a/src/zoom.js b/src/zoom.js
index 735483774..3b9d23906 100644
--- a/src/zoom.js
+++ b/src/zoom.js
@@ -10,7 +10,7 @@ import noevent, {nopropagation} from "./noevent";
 
 // Ignore right-click, since that should open the context menu.
 function defaultFilter() {
-  return !event.button;
+  return !event.ctrlKey && !event.button;
 }
 
 function defaultExtent() {