diff --git a/lib/sectorset.h b/lib/sectorset.h
index b7d4e6db..3bd46cb9 100644
--- a/lib/sectorset.h
+++ b/lib/sectorset.h
@@ -5,8 +5,9 @@ class Sector;
 
 class SectorSet
 {
-private:
+public:
 	typedef std::tuple<int, int, int> key_t;
+
 public:
 	static key_t keyof(int track, int head, int sector)
 	{ return std::tuple<int, int, int>(track, head, sector); }
diff --git a/src/fe-writebrother.cc b/src/fe-writebrother.cc
index ba8b05ce..7df7eed3 100644
--- a/src/fe-writebrother.cc
+++ b/src/fe-writebrother.cc
@@ -81,7 +81,7 @@ int main(int argc, const char* argv[])
 				double dataMs = headerMs + postHeaderSpacingMs;
 				unsigned dataCursor = dataMs*1e3 / clockRateUs;
 
-				auto& sectorData = allSectors[{track, 0, sectorId}];
+				auto& sectorData = allSectors[SectorSet::key_t {track, 0, sectorId}];
 
 				fillBitmapTo(bits, cursor, headerCursor, { true, false });
 				writeBrotherSectorHeader(bits, cursor, track, sectorId);