diff --git a/src/subdataframe/subdataframe.jl b/src/subdataframe/subdataframe.jl
index 5436fc7e0b..75a6481bf2 100644
--- a/src/subdataframe/subdataframe.jl
+++ b/src/subdataframe/subdataframe.jl
@@ -5,22 +5,20 @@
 ##
 ##############################################################################
 
-include_string("""
-        immutable SubDataFrame{T <: AbstractVector{Int}} <: AbstractDataFrame
-            parent::DataFrame
-            rows::T # maps from subdf row indexes to parent row indexes
-
-            function SubDataFrame{T}(parent::DataFrame, rows::T) where {T <: AbstractVector{Int}}
-                if length(rows) > 0
-                    rmin, rmax = extrema(rows)
-                    if rmin < 1 || rmax > size(parent, 1)
-                        throw(BoundsError())
-                    end
-                end
-                new(parent, rows)
+struct SubDataFrame{T <: AbstractVector{Int}} <: AbstractDataFrame
+    parent::DataFrame
+    rows::T # maps from subdf row indexes to parent row indexes
+
+    function SubDataFrame{T}(parent::DataFrame, rows::T) where {T <: AbstractVector{Int}}
+        if length(rows) > 0
+            rmin, rmax = extrema(rows)
+            if rmin < 1 || rmax > size(parent, 1)
+                throw(BoundsError())
             end
         end
-    """)
+        new(parent, rows)
+    end
+end
 
 """
 A view of row subsets of an AbstractDataFrame