diff --git a/contrib/prtview/LoadPortalFileDialog.cpp b/contrib/prtview/LoadPortalFileDialog.cpp
index 00be59b2..4576ebd2 100644
--- a/contrib/prtview/LoadPortalFileDialog.cpp
+++ b/contrib/prtview/LoadPortalFileDialog.cpp
@@ -24,6 +24,7 @@
 
 #include "stream/stringstream.h"
 #include "convert.h"
+#include "os/path.h"
 
 #include "qerplugin.h"
 
@@ -51,7 +52,6 @@ bool DoLoadPortalFileDialog(){
 		auto vbox = new QVBoxLayout( &dialog );
 		{
 			vbox->addWidget( line = new QLineEdit );
-			line->setMaxLength( std::size( portals.fn ) - 1 );
 			auto button = line->addAction( QApplication::style()->standardIcon( QStyle::SP_FileDialogStart ), QLineEdit::ActionPosition::TrailingPosition );
 			QObject::connect( button, &QAction::triggered, [line](){
 				if ( const char* filename = GlobalRadiant().m_pfnFileDialog( g_pRadiantWnd, true, "Locate portal (.prt) file", line->text().toLatin1().constData(), 0, true, false, false ) )
@@ -71,18 +71,14 @@ bool DoLoadPortalFileDialog(){
 	}
 
 
-	strcpy( portals.fn, GlobalRadiant().getMapName() );
-	char* fn = strrchr( portals.fn, '.' );
-	if ( fn != NULL ) {
-		strcpy( fn, ".prt" );
-	}
+	portals.fn = StringOutputStream( 256 )( PathExtensionless( GlobalRadiant().getMapName() ), ".prt" );
 
-	line->setText( portals.fn );
+	line->setText( portals.fn.c_str() );
 	check3d->setChecked( portals.show_3d );
 	check2d->setChecked( portals.show_2d );
 
 	if ( dialog.exec() ) {
-		strcpy( portals.fn, line->text().toLatin1().constData() );
+		portals.fn = line->text().toLatin1().constData();
 
 		portals.Purge();
 
diff --git a/contrib/prtview/portals.cpp b/contrib/prtview/portals.cpp
index 7a5e41ab..0ae278bc 100644
--- a/contrib/prtview/portals.cpp
+++ b/contrib/prtview/portals.cpp
@@ -135,7 +135,7 @@ void CPortals::Load(){
 
 	FILE *in;
 
-	in = fopen( fn, "rt" );
+	in = fopen( fn.c_str(), "rt" );
 
 	if ( in == NULL ) {
 		globalErrorStream() << "  ERROR - could not open file.\n";
diff --git a/contrib/prtview/portals.h b/contrib/prtview/portals.h
index 6770f8ae..43293a7b 100644
--- a/contrib/prtview/portals.h
+++ b/contrib/prtview/portals.h
@@ -22,6 +22,7 @@
 #include "irender.h"
 #include "renderable.h"
 #include "math/vector.h"
+#include "string/string.h"
 #include <vector>
 
 
@@ -45,12 +46,6 @@ public:
 	bool Build( char *def );
 };
 
-#ifdef PATH_MAX
-#define PRTVIEW_PATH_MAX PATH_MAX
-#else
-#define PRTVIEW_PATH_MAX 260
-#endif
-
 using PackedColour = std::uint32_t;
 #define RGB_PACK( r, g, b ) ( (std::uint32_t)( ( (std::uint8_t)( r ) | ( (std::uint16_t)( (std::uint8_t)( g ) ) << 8 ) ) | ( ( (std::uint32_t)(std::uint8_t)( b ) ) << 16 ) ) )
 #define RGB_UNPACK_R( rgb )      ( (std::uint8_t)( rgb ) )
@@ -75,7 +70,7 @@ public:
 
 	void FixColors();
 
-	char fn[PRTVIEW_PATH_MAX];
+	CopiedString fn;
 
 	int zbuffer;
 	bool polygons;