diff --git a/ggplot/stats/stat.py b/ggplot/stats/stat.py
index 39d51a966..1ee8b8be8 100644
--- a/ggplot/stats/stat.py
+++ b/ggplot/stats/stat.py
@@ -73,7 +73,8 @@ def use_defaults(self, data):
                    set(data.columns))
 
         for ae in missing:
-            data[ae] = self.DEFAULT_AES[ae]
+            if self.DEFAULT_AES[ae] is not None:
+                data[ae] = self.DEFAULT_AES[ae]
 
         missing = (self.aes_params.viewkeys() -
                    set(data.columns))
diff --git a/ggplot/stats/stat_bin.py b/ggplot/stats/stat_bin.py
index 2751ad3cc..1fdae1dd8 100644
--- a/ggplot/stats/stat_bin.py
+++ b/ggplot/stats/stat_bin.py
@@ -18,7 +18,7 @@ class stat_bin(stat):
                       'width': 0.9, 'drop': False, 'right': False,
                       'binwidth': None, 'bins': None,
                       'origin': None, 'breaks': None}
-    DEFAULT_AES = {'y': '..count..', 'weight': 1}
+    DEFAULT_AES = {'y': '..count..', 'weight': None}
     CREATES = {'y', 'width'}
 
     def setup_params(self, data):
diff --git a/ggplot/stats/stat_bin_2d.py b/ggplot/stats/stat_bin_2d.py
index e053b148f..b4378b5b9 100644
--- a/ggplot/stats/stat_bin_2d.py
+++ b/ggplot/stats/stat_bin_2d.py
@@ -19,7 +19,7 @@ class stat_bin_2d(stat):
     DEFAULT_PARAMS = {'geom': 'rect', 'position': 'identity',
                       'bins': 30, 'breaks': None, 'origin': None,
                       'binwidth': None, 'drop': True}
-    DEFAULT_AES = {'fill': '..count..', 'weight': 1}
+    DEFAULT_AES = {'fill': '..count..', 'weight': None}
     CREATES = {'xmin', 'xmax', 'ymin', 'ymax', 'fill'}
 
     def setup_params(self, data):
diff --git a/ggplot/stats/stat_ydensity.py b/ggplot/stats/stat_ydensity.py
index cf30a479f..a311b622d 100644
--- a/ggplot/stats/stat_ydensity.py
+++ b/ggplot/stats/stat_ydensity.py
@@ -16,7 +16,7 @@ class stat_ydensity(stat):
                       'adjust': 1, 'kernel': 'gaussian',
                       'n': 1024, 'trim': True,
                       'scale': 'area'}
-    DEFAULT_AES = {'weight': 1}
+    DEFAULT_AES = {'weight': None}
 
     def setup_params(self, data):
         params = self.params.copy()