diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
index d99323d0608e..bbc489502262 100644
--- a/lib/matplotlib/artist.py
+++ b/lib/matplotlib/artist.py
@@ -1042,8 +1042,9 @@ def format_cursor_data(self, data):
             data[0]
         except (TypeError, IndexError):
             data = [data]
-        return ', '.join('{:0.3g}'.format(item) for item in data if
-                isinstance(item, (np.floating, np.integer, int, float)))
+        data_str = ', '.join('{:0.3g}'.format(item) for item in data if
+                   isinstance(item, (np.floating, np.integer, int, float)))
+        return "[" + data_str + "]"
 
     @property
     def mouseover(self):
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
index fc92f6dd1869..ddd4e6d3b0ba 100644
--- a/lib/matplotlib/backend_bases.py
+++ b/lib/matplotlib/backend_bases.py
@@ -2860,7 +2860,9 @@ def mouse_move(self, event):
                     if a is not event.inaxes.patch:
                         data = a.get_cursor_data(event)
                         if data is not None:
-                            s += ' [%s]' % a.format_cursor_data(data)
+                            data_str = a.format_cursor_data(data)
+                            if data_str is not None:
+                                s = s + ' ' + data_str
 
                 if len(self.mode):
                     self.set_message('%s, %s' % (self.mode, s))
diff --git a/lib/matplotlib/backend_tools.py b/lib/matplotlib/backend_tools.py
index 3fcb3cb5c6a1..9c9249da8fb8 100644
--- a/lib/matplotlib/backend_tools.py
+++ b/lib/matplotlib/backend_tools.py
@@ -344,7 +344,9 @@ def send_message(self, event):
                     if a is not event.inaxes.patch:
                         data = a.get_cursor_data(event)
                         if data is not None:
-                            s += ' [%s]' % a.format_cursor_data(data)
+                            data_str = a.format_cursor_data(data)
+                            if data_str is not None:
+                                s = s + ' ' + data_str
 
                 message = s
         self.toolmanager.message_event(message, self)