diff --git a/stepmania/src/RageFile.cpp b/stepmania/src/RageFile.cpp
index e952b437b7..10931dae5a 100644
--- a/stepmania/src/RageFile.cpp
+++ b/stepmania/src/RageFile.cpp
@@ -319,7 +319,7 @@ int RageFile::SeekCur( int offset )
 	return m_FilePos;
 }
 
-int RageFile::GetFileSize()
+int RageFile::GetFileSize() const
 {
 	if( !IsOpen() )
 		RageException::Throw("\"%s\" is not open.", GetPath().c_str());
@@ -327,7 +327,10 @@ int RageFile::GetFileSize()
 	if( !(m_Mode&READ) )
 		RageException::Throw("\"%s\" is not open for reading; can't GetFileSize", GetPath().c_str());
 
-	return m_File->GetFileSize();
+	/* GetFileSize() may need to do non-const-like things--the default implementation reads
+	 * until the end of file to emulate it.  However, it should always restore the state to
+	 * the way it was, so pretend it's const. */
+	return const_cast<RageFileObj*>(m_File)->GetFileSize();
 }
 
 void RageFile::Rewind()
diff --git a/stepmania/src/RageFile.h b/stepmania/src/RageFile.h
index 04ac76e3e7..190a8bd79e 100644
--- a/stepmania/src/RageFile.h
+++ b/stepmania/src/RageFile.h
@@ -56,7 +56,7 @@ public:
 	int Tell() const { return m_FilePos; }
 	int Seek( int offset );
 	int SeekCur( int offset );
-	int GetFileSize();
+	int GetFileSize() const;
 	void Rewind();
     
 	/* Raw I/O: */