diff --git a/arch/micropolis/decoder.cc b/arch/micropolis/decoder.cc
index 7b817caa..116ac6b1 100644
--- a/arch/micropolis/decoder.cc
+++ b/arch/micropolis/decoder.cc
@@ -6,6 +6,7 @@
 #include "micropolis.h"
 #include "bytes.h"
 #include "fmt/format.h"
+#include "lib/decoders/decoders.pb.h"
 
 /* The sector has a preamble of MFM 0x00s and uses 0xFF as a sync pattern. */
 static const FluxPattern SECTOR_SYNC_PATTERN(32, 0xaaaa5555);
@@ -28,7 +29,8 @@ class MicropolisDecoder : public AbstractDecoder
 {
 public:
 	MicropolisDecoder(const DecoderProto& config):
-		AbstractDecoder(config)
+		AbstractDecoder(config),
+		_config(config.micropolis())
 	{}
 
 	RecordType advanceToNextRecord()
@@ -59,13 +61,21 @@ public:
 			return;
 
 		br.read(10);  /* OS data or padding */
-		_sector->data = br.read(256);
+		auto data = br.read(256);
 		uint8_t wantChecksum = br.read_8();
 		uint8_t gotChecksum = micropolisChecksum(bytes.slice(1, 2+266));
 		br.read(5);  /* 4 byte ECC and ECC-present flag */
 
+		if (_config.sector_output_size() == 256)
+			_sector->data = data;
+		else if (_config.sector_output_size() == MICROPOLIS_ENCODED_SECTOR_SIZE)
+			_sector->data = bytes;
+		else
+			Error() << "Sector output size may only be 256 or 275";
 		_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
 	}
+private:
+	const MicropolisDecoderProto& _config;
 };
 
 std::unique_ptr<AbstractDecoder> createMicropolisDecoder(const DecoderProto& config)
diff --git a/arch/micropolis/encoder.cc b/arch/micropolis/encoder.cc
index 14b19911..77719222 100644
--- a/arch/micropolis/encoder.cc
+++ b/arch/micropolis/encoder.cc
@@ -19,7 +19,15 @@ static void write_sector(std::vector<bool>& bits, unsigned& cursor, const std::s
 		fullSector->push_back(0);
 	Bytes sectorData;
 	if (sector->data.size() == MICROPOLIS_ENCODED_SECTOR_SIZE)
+	{
+		if (sector->data[0] != 0xFF)
+			Error() << "275 byte sector doesn't start with sync byte 0xFF. Corrupted sector";
+		uint8_t wantChecksum = sector->data[1+2+266];
+		uint8_t gotChecksum = micropolisChecksum(sector->data.slice(1, 2+266));
+		if (wantChecksum != gotChecksum)
+			std::cerr << "Warning: checksum incorrect. Sector: " << sector->logicalSector << std::endl;
 		sectorData = sector->data;
+	}
 	else
 	{
 		ByteWriter writer(sectorData);
diff --git a/arch/micropolis/micropolis.proto b/arch/micropolis/micropolis.proto
index 417a9089..8d383ac2 100644
--- a/arch/micropolis/micropolis.proto
+++ b/arch/micropolis/micropolis.proto
@@ -1,5 +1,11 @@
 syntax = "proto2";
 
-message MicropolisDecoderProto {}
+import "lib/common.proto";
+
+message MicropolisDecoderProto {
+	optional int32 sector_output_size = 1 [default = 256,
+		(help) = "How much of the raw sector should be saved. Must be 256 or 275"];
+}
+
 message MicropolisEncoderProto {}
 
diff --git a/mkninja.sh b/mkninja.sh
index 6725b0d8..1078c501 100644
--- a/mkninja.sh
+++ b/mkninja.sh
@@ -422,6 +422,7 @@ FORMATS="\
     mac400 \
     mac800 \
     micropolis \
+    micropolis275 \
     mx \
     northstar175 \
     northstar350 \
diff --git a/src/formats/micropolis275.textpb b/src/formats/micropolis275.textpb
new file mode 100644
index 00000000..d0f7c191
--- /dev/null
+++ b/src/formats/micropolis275.textpb
@@ -0,0 +1,54 @@
+comment: 'Micropolis MetaFloppy 630kB 5.25" DSDD hard-sectored'
+
+flux_source {
+	drive {
+		hard_sector_count: 16
+	}
+}
+
+flux_sink {
+	drive {
+		hard_sector_count: 16
+	}
+}
+
+image_reader {
+	filename: "micropolis.img"
+	img {
+		tracks: 77
+		sides: 2
+		trackdata {
+			sector_size: 275
+			sector_range {
+				start_sector: 0
+				sector_count: 16
+			}
+		}
+	}
+}
+
+image_writer {
+	filename: "micropolis.img"
+	img {}
+}
+
+encoder {
+	micropolis {}
+}
+
+decoder {
+	micropolis {
+		sector_output_size: 275
+	}
+}
+
+cylinders {
+	start: 0
+	end: 76
+}
+
+heads {
+	start: 0
+	end: 1
+}
+