diff --git a/src/Canvas.cc b/src/Canvas.cc
index b6ef59a..c727416 100644
--- a/src/Canvas.cc
+++ b/src/Canvas.cc
@@ -13,6 +13,8 @@
 #include <node_buffer.h>
 #include <node_version.h>
 
+Persistent<FunctionTemplate> Canvas::constructor;
+
 /*
  * Buffer data pointer access.
  */
diff --git a/src/CanvasGradient.cc b/src/CanvasGradient.cc
index 857ff15..5419cc2 100644
--- a/src/CanvasGradient.cc
+++ b/src/CanvasGradient.cc
@@ -8,6 +8,8 @@
 #include "Canvas.h"
 #include "CanvasGradient.h"
 
+Persistent<FunctionTemplate> Gradient::constructor;
+
 /*
  * Initialize CanvasGradient.
  */
diff --git a/src/CanvasRenderingContext2d.cc b/src/CanvasRenderingContext2d.cc
index 7261ac4..99ff7fc 100644
--- a/src/CanvasRenderingContext2d.cc
+++ b/src/CanvasRenderingContext2d.cc
@@ -14,6 +14,8 @@
 #include "CanvasRenderingContext2d.h"
 #include "CanvasGradient.h"
 
+Persistent<FunctionTemplate> Context2d::constructor;
+
 /*
  * Set RGBA.
  */
diff --git a/src/Image.cc b/src/Image.cc
index d20befb..7e6315f 100644
--- a/src/Image.cc
+++ b/src/Image.cc
@@ -10,6 +10,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+Persistent<FunctionTemplate> Image::constructor;
+
 /*
  * Initialize Image.
  */
diff --git a/src/ImageData.cc b/src/ImageData.cc
index b5bb653..08bed4f 100644
--- a/src/ImageData.cc
+++ b/src/ImageData.cc
@@ -7,6 +7,8 @@
 
 #include "ImageData.h"
 
+Persistent<FunctionTemplate> ImageData::constructor;
+
 /*
  * Initialize ImageData.
  */
diff --git a/src/PixelArray.cc b/src/PixelArray.cc
index b6250f0..9e4eaa0 100644
--- a/src/PixelArray.cc
+++ b/src/PixelArray.cc
@@ -9,6 +9,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+Persistent<FunctionTemplate> PixelArray::constructor;
+
 /*
  * Initialize PixelArray.
  */