diff --git a/image/codecs/truemotion1.cpp b/image/codecs/truemotion1.cpp
index 1302d72e2f6f..b5f7c76f6bf2 100644
--- a/image/codecs/truemotion1.cpp
+++ b/image/codecs/truemotion1.cpp
@@ -90,14 +90,9 @@ static const CompressionType compressionTypes[17] = {
 
 TrueMotion1Decoder::TrueMotion1Decoder(uint16 width, uint16 height) {
 	_surface = new Graphics::Surface();
-	_width = width;
-	_height = height;
-
 	_surface->create(width, height, getPixelFormat());
 
-	// there is a vertical predictor for each pixel in a line; each vertical
-	// predictor is 0 to start with
-	_vertPred = new uint32[_width];
+	_vertPred = 0;
 
 	_buf = _mbChangeBits = _indexStream = 0;
 	_lastDeltaset = _lastVectable = -1;
@@ -170,11 +165,6 @@ void TrueMotion1Decoder::decodeHeader(Common::SeekableReadStream &stream) {
 	byte headerBuffer[128];  // logical maximum size of the header
 	const byte *selVectorTable;
 
-	// There is 1 change bit per 4 pixels, so each change byte represents
-	// 32 pixels; divide width by 4 to obtain the number of change bits and
-	// then round up to the nearest byte.
-	_mbChangeBitsRowSize = ((_width >> 2) + 7) >> 3;
-
 	_header.headerSize = ((_buf[0] >> 5) | (_buf[0] << 3)) & 0x7f;
 
 	if (_buf[0] < 0x10)
@@ -196,6 +186,17 @@ void TrueMotion1Decoder::decodeHeader(Common::SeekableReadStream &stream) {
 	_header.flags = headerBuffer[11];
 	_header.control = headerBuffer[12];
 
+	if (!_vertPred) {
+		// there is a vertical predictor for each pixel in a line; each vertical
+		// predictor is 0 to start with
+		_vertPred = new uint32[_header.xsize];
+	}
+
+	// There is 1 change bit per 4 pixels, so each change byte represents
+	// 32 pixels; divide width by 4 to obtain the number of change bits and
+	// then round up to the nearest byte.
+	_mbChangeBitsRowSize = ((_header.xsize >> 2) + 7) >> 3;
+
 	// Version 2
 	if (_header.version >= 2) {
 		if (_header.headerType > 3) {
@@ -240,7 +241,7 @@ void TrueMotion1Decoder::decodeHeader(Common::SeekableReadStream &stream) {
 		_indexStream = _mbChangeBits;
 	} else {
 		// one change bit per 4x4 block
-		_indexStream = _mbChangeBits + _mbChangeBitsRowSize * (_height >> 2);
+		_indexStream = _mbChangeBits + _mbChangeBitsRowSize * (_header.ysize >> 2);
 	}
 
 	_indexStreamSize = stream.size() - (_indexStream - _buf);
@@ -306,11 +307,11 @@ void TrueMotion1Decoder::decode16() {
 	int index;
 
 	// clean out the line buffer
-	memset(_vertPred, 0, _width * 4);
+	memset(_vertPred, 0, _header.xsize * 4);
 
 	GET_NEXT_INDEX();
 
-	for (int y = 0; y < _height; y++) {
+	for (int y = 0; y < _header.ysize; y++) {
 		// re-init variables for the next line iteration
 		uint32 horizPred = 0;
 		uint32 *currentPixelPair = (uint32 *)_surface->getBasePtr(0, y);
@@ -319,7 +320,7 @@ void TrueMotion1Decoder::decode16() {
 		byte mbChangeByte = _mbChangeBits[mbChangeIndex++];
 		byte mbChangeByteMask = 1;
 
-		for (int pixelsLeft = _width; pixelsLeft > 0; pixelsLeft -= 4) {
+		for (int pixelsLeft = _header.xsize; pixelsLeft > 0; pixelsLeft -= 4) {
 			if (keyframe || (mbChangeByte & mbChangeByteMask) == 0) {
 				switch (y & 3) {
 				case 0:
diff --git a/image/codecs/truemotion1.h b/image/codecs/truemotion1.h
index 12570f066cef..bbbcd6d6be55 100644
--- a/image/codecs/truemotion1.h
+++ b/image/codecs/truemotion1.h
@@ -54,7 +54,6 @@ class TrueMotion1Decoder : public Codec {
 	byte *_buf, *_mbChangeBits, *_indexStream;
 	int _indexStreamSize;
 
-	uint16 _width, _height;
 	int _flags;
 
 	struct PredictorTableEntry {