diff --git a/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/ByteViewerComponent.java b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/ByteViewerComponent.java
index fa1bf91008..bf588e1ed1 100644
--- a/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/ByteViewerComponent.java
+++ b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/ByteViewerComponent.java
@@ -606,6 +606,7 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 
 	/**
 	 * Convert the cursor location to a byte block and an offset.
+	 * @return the cursor location to a byte block and an offset.
 	 */
 	ByteBlockInfo getViewerCursorLocation() {
 		FieldLocation loc = getCursorLocation();
@@ -634,11 +635,10 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 		if (info == null) {
 			return null;
 		}
-		ByteBlock block = info.getBlock();
 		BigInteger offset = info.getOffset();
 		int byteOffset = model.getByteOffset(info.getBlock(), pos);
 		offset = offset.add(BigInteger.valueOf(byteOffset));
-		return new ByteBlockInfo(block, offset, loc.getCol());
+		return new ByteBlockInfo(info.getBlock(), offset, loc.getCol());
 	}
 
 	DataFormatModel getDataModel() {
@@ -764,7 +764,7 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 		layoutModel.setFactorys(fieldFactories, model, charWidth);
 	}
 
-	private ByteBlockInfo getBlockInfoForSelectionStart(FieldLocation loc) {
+	private IndexedByteBlockInfo getBlockInfoForSelectionStart(FieldLocation loc) {
 		BigInteger index = loc.getIndex();
 		int fieldNum = loc.getFieldNum();
 
@@ -778,7 +778,7 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 		return indexMap.getBlockInfo(index, offset);
 	}
 
-	private ByteBlockInfo getBlockInfoForSelectionEnd(FieldLocation loc) {
+	private IndexedByteBlockInfo getBlockInfoForSelectionEnd(FieldLocation loc) {
 		BigInteger lineIndex = loc.getIndex();
 		int fieldNum = loc.getFieldNum();
 
@@ -812,10 +812,17 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 		return indexMap.getBlockInfo(lineIndex, lastByteInSelectionOnLine);
 	}
 
-	private void addByteBlockRange(ByteBlockSelection sel, ByteBlockInfo start, ByteBlockInfo end) {
+	private void addByteBlockRange(ByteBlockSelection sel, IndexedByteBlockInfo start,
+			IndexedByteBlockInfo end) {
 		if (start == null || end == null) {
 			return;
 		}
+
+		// this should only happen when both the start and end are on the same separator line
+		if (start.compareTo(end) > 0) {
+			return;
+		}
+
 		ByteBlock startBlock = start.getBlock();
 		ByteBlock endBlock = end.getBlock();
 
@@ -849,8 +856,8 @@ public class ByteViewerComponent extends FieldPanel implements FieldMouseListene
 
 		for (int i = 0; i < count; i++) {
 			FieldRange range = fieldSelection.getFieldRange(i);
-			ByteBlockInfo start = getBlockInfoForSelectionStart(range.getStart());
-			ByteBlockInfo end = getBlockInfoForSelectionEnd(range.getEnd());
+			IndexedByteBlockInfo start = getBlockInfoForSelectionStart(range.getStart());
+			IndexedByteBlockInfo end = getBlockInfoForSelectionEnd(range.getEnd());
 			addByteBlockRange(blockSelection, start, end);
 		}
 
diff --git a/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/IndexMap.java b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/IndexMap.java
index cc5e792d65..56a201f55a 100644
--- a/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/IndexMap.java
+++ b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/IndexMap.java
@@ -100,7 +100,7 @@ public class IndexMap {
 	 * @return The ByteBlockInfo object that contains the block and offset into that block
 	 * that is the resulting byte value.
 	 */
-	ByteBlockInfo getBlockInfo(BigInteger index, int fieldOffset) {
+	IndexedByteBlockInfo getBlockInfo(BigInteger index, int fieldOffset) {
 		SortedMap<BigInteger, BlockInfo> tailMap = blockInfoMap.tailMap(index);
 		if (tailMap.isEmpty()) {
 			return null;
@@ -109,7 +109,8 @@ public class IndexMap {
 		BigInteger byteIndex = index.multiply(bytesInLine).add(BigInteger.valueOf(fieldOffset));
 		if ((byteIndex.compareTo(blockInfo.blockStart) >= 0) &&
 			(byteIndex.compareTo(blockInfo.blockEnd) < 0)) {
-			return new ByteBlockInfo(blockInfo.block, byteIndex.subtract(blockInfo.blockStart));
+			return new IndexedByteBlockInfo(index, blockInfo.block,
+				byteIndex.subtract(blockInfo.blockStart), 0);
 		}
 		return null;
 	}
@@ -257,12 +258,12 @@ public class IndexMap {
 		while (iterator.hasNext()) {
 			BlockInfo next = iterator.next();
 			if (next.block == endBlock) {
-				break;
+				return byteBlocks;
 			}
 			byteBlocks.add(next.block);
 		}
-		return byteBlocks;
-
+		// didn't find the end, so the end must have been before the start, so return empty list
+		return List.of();
 	}
 
 }
diff --git a/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/format/IndexedByteBlockInfo.java b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/format/IndexedByteBlockInfo.java
new file mode 100644
index 0000000000..e0fa9d0d2b
--- /dev/null
+++ b/Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/format/IndexedByteBlockInfo.java
@@ -0,0 +1,47 @@
+/* ###
+ * IP: GHIDRA
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package ghidra.app.plugin.core.format;
+
+import java.math.BigInteger;
+
+/**
+ * This is a ByteBlockInfo that also includes line index information. With the extra line index 
+ * information, this object can be ordered and therefore, can implement {@link Comparable} 
+ */
+public class IndexedByteBlockInfo extends ByteBlockInfo
+		implements Comparable<IndexedByteBlockInfo> {
+
+	private BigInteger lineIndex;
+
+	public IndexedByteBlockInfo(BigInteger lineIndex, ByteBlock block, BigInteger offset,
+			int column) {
+		super(block, offset, column);
+		this.lineIndex = lineIndex;
+	}
+
+	@Override
+	public int compareTo(IndexedByteBlockInfo o) {
+		int result = lineIndex.compareTo(o.lineIndex);
+		if (result == 0) {
+			result = getOffset().compareTo(o.getOffset());
+		}
+		if (result == 0) {
+			return Integer.compare(getColumn(), o.getColumn());
+		}
+		return result;
+	}
+
+}