diff --git a/src/dobjtype.cpp b/src/dobjtype.cpp
index 4d6056c3a4..6d459dc274 100644
--- a/src/dobjtype.cpp
+++ b/src/dobjtype.cpp
@@ -223,7 +223,7 @@ void PType::SetValue(void *addr, int val)
 //
 //==========================================================================
 
-int PType::GetValueInt(void *addr)
+int PType::GetValueInt(void *addr) const
 {
 	assert(0 && "Cannot get value for this type");
 	return 0;
@@ -420,7 +420,7 @@ void PInt::SetValue(void *addr, int val)
 //
 //==========================================================================
 
-int PInt::GetValueInt(void *addr)
+int PInt::GetValueInt(void *addr) const
 {
 	assert(((intptr_t)addr & (Align - 1)) == 0 && "unaligned address");
 	if (Size == 4)
@@ -498,7 +498,7 @@ void PFloat::SetValue(void *addr, int val)
 //
 //==========================================================================
 
-int PFloat::GetValueInt(void *addr)
+int PFloat::GetValueInt(void *addr) const
 {
 	assert(((intptr_t)addr & (Align - 1)) == 0 && "unaligned address");
 	if (Size == 4)
diff --git a/src/dobjtype.h b/src/dobjtype.h
index a51eaa16df..053b93072d 100644
--- a/src/dobjtype.h
+++ b/src/dobjtype.h
@@ -172,7 +172,8 @@ public:
 	virtual void SetValue(void *addr, int val);
 
 	// Gets the value of a variable of this type at (addr)
-	virtual int GetValueInt(void *addr);
+	virtual int GetValueInt(void *addr) const;
+
 
 	// Returns true if this type matches the two identifiers. Referring to the
 	// above table, any type is identified by at most two characteristics. Each
@@ -227,7 +228,7 @@ public:
 	PInt(unsigned int size, bool unsign);
 
 	virtual void SetValue(void *addr, int val);
-	virtual int GetValueInt(void *addr);
+	virtual int GetValueInt(void *addr) const;
 
 	bool Unsigned;
 protected:
@@ -241,7 +242,7 @@ public:
 	PFloat(unsigned int size);
 
 	virtual void SetValue(void *addr, int val);
-	virtual int GetValueInt(void *addr);
+	virtual int GetValueInt(void *addr) const;
 protected:
 	PFloat();
 };