diff --git a/content/svg/content/src/nsSVGTextContentElement.cpp b/content/svg/content/src/nsSVGTextContentElement.cpp
index bfc10b2cac60..b808fdc7003b 100644
--- a/content/svg/content/src/nsSVGTextContentElement.cpp
+++ b/content/svg/content/src/nsSVGTextContentElement.cpp
@@ -37,6 +37,9 @@
  * ***** END LICENSE BLOCK ***** */
 
 #include "nsSVGTextContentElement.h"
+#include "DOMSVGPoint.h"
+
+using namespace mozilla;
 
 /* readonly attribute nsIDOMSVGAnimatedLength textLength; */
 NS_IMETHODIMP nsSVGTextContentElement::GetTextLength(nsIDOMSVGAnimatedLength * *aTextLength)
@@ -143,8 +146,8 @@ NS_IMETHODIMP nsSVGTextContentElement::GetRotationOfChar(PRUint32 charnum, float
 /* long getCharNumAtPosition (in nsIDOMSVGPoint point); */
 NS_IMETHODIMP nsSVGTextContentElement::GetCharNumAtPosition(nsIDOMSVGPoint *point, PRInt32 *_retval)
 {
-  // null check when implementing - this method can be used by scripts!
-  if (!point)
+  nsCOMPtr<DOMSVGPoint> p = do_QueryInterface(point);
+  if (!p)
     return NS_ERROR_DOM_SVG_WRONG_TYPE_ERR;
 
   *_retval = -1;
diff --git a/content/svg/content/src/nsSVGTextElement.cpp b/content/svg/content/src/nsSVGTextElement.cpp
index 0b4b4e4a35a3..bd4eff0f7938 100644
--- a/content/svg/content/src/nsSVGTextElement.cpp
+++ b/content/svg/content/src/nsSVGTextElement.cpp
@@ -50,6 +50,7 @@
 #include "SVGNumberList.h"
 #include "SVGAnimatedNumberList.h"
 #include "DOMSVGAnimatedNumberList.h"
+#include "DOMSVGPoint.h"
 
 using namespace mozilla;
 
@@ -323,7 +324,8 @@ nsSVGTextElement::GetRotationOfChar(PRUint32 charnum, float *_retval)
 NS_IMETHODIMP
 nsSVGTextElement::GetCharNumAtPosition(nsIDOMSVGPoint *point, PRInt32 *_retval)
 {
-  if (!point)
+  nsCOMPtr<DOMSVGPoint> p = do_QueryInterface(point);
+  if (!p)
     return NS_ERROR_DOM_SVG_WRONG_TYPE_ERR;
 
   *_retval = -1;