diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 64e3d60e1fe14..40f2761b44dea 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -3093,10 +3093,11 @@ def astype(self, dtype, copy=True, raise_on_error=True, **kwargs):
                     'invoked on Series and DataFrames. A single dtype must be '
                     'specified when invoked on a Panel.'
                 )
-            for col_name in dtype.keys():
-                if col_name not in self:
-                    raise KeyError('Only a column name can be used for the '
-                                   'key in a dtype mappings argument.')
+            if raise_on_error:
+                for col_name in dtype.keys():
+                    if col_name not in self:
+                        raise KeyError('Only a column name can be used for the '
+                                       'key in a dtype mappings argument.')
             from pandas import concat
             results = []
             for col_name, col in self.iteritems():