diff --git a/ebml/EbmlSInteger.h b/ebml/EbmlSInteger.h
index ea40ca7..62fed03 100644
--- a/ebml/EbmlSInteger.h
+++ b/ebml/EbmlSInteger.h
@@ -71,10 +71,10 @@ class EBML_DLL_API EbmlSInteger : public EbmlElement {
 
 		virtual bool IsSmallerThan(const EbmlElement *Cmp) const;
 
-		operator int8();
-		operator int16();
-		operator int32();
-		operator int64();
+		operator int8() const;
+		operator int16() const;
+		operator int32() const;
+		operator int64() const;
 
 		void SetDefaultValue(int64 aValue) {assert(!DefaultISset()); DefaultValue = aValue; SetDefaultIsSet();}
 
diff --git a/src/EbmlSInteger.cpp b/src/EbmlSInteger.cpp
index b8b031b..9da6704 100644
--- a/src/EbmlSInteger.cpp
+++ b/src/EbmlSInteger.cpp
@@ -55,10 +55,10 @@ EbmlSInteger::EbmlSInteger(const EbmlSInteger & ElementToClone)
 {
 }
 
-EbmlSInteger::operator int8() {return  int8(Value);}
-EbmlSInteger::operator int16() {return int16(Value);}
-EbmlSInteger::operator int32() {return int32(Value);}
-EbmlSInteger::operator int64() {return Value;}
+EbmlSInteger::operator int8() const {return  int8(Value);}
+EbmlSInteger::operator int16() const {return int16(Value);}
+EbmlSInteger::operator int32() const {return int32(Value);}
+EbmlSInteger::operator int64() const {return Value;}
 
 /*!
 	\todo handle exception on errors