diff --git a/lib/ConcatSource.js b/lib/ConcatSource.js
index c393fa1..f10463c 100644
--- a/lib/ConcatSource.js
+++ b/lib/ConcatSource.js
@@ -212,24 +212,18 @@ class ConcatSource extends Source {
 							? -1
 							: nameIndexMapping[nameIndex];
 					lastMappingLine = resultSourceIndex < 0 ? 0 : generatedLine;
+					let _chunk;
+					// When using finalSource, we process the entire source code at once at the end, rather than chunk by chunk
 					if (finalSource) {
 						if (chunk !== undefined) code += chunk;
-						if (resultSourceIndex >= 0) {
-							onChunk(
-								undefined,
-								line,
-								column,
-								resultSourceIndex,
-								originalLine,
-								originalColumn,
-								resultNameIndex,
-							);
-						}
-					} else if (resultSourceIndex < 0) {
-						onChunk(chunk, line, column, -1, -1, -1, -1);
+					} else {
+						_chunk = chunk;
+					}
+					if (resultSourceIndex < 0) {
+						onChunk(_chunk, line, column, -1, -1, -1, -1);
 					} else {
 						onChunk(
-							chunk,
+							_chunk,
 							line,
 							column,
 							resultSourceIndex,
diff --git a/lib/helpers/streamChunksOfCombinedSourceMap.js b/lib/helpers/streamChunksOfCombinedSourceMap.js
index 8a2fd2b..d1355f1 100644
--- a/lib/helpers/streamChunksOfCombinedSourceMap.js
+++ b/lib/helpers/streamChunksOfCombinedSourceMap.js
@@ -51,7 +51,7 @@ const streamChunksOfCombinedSourceMap = (
 	const nameIndexMapping = [];
 	/** @type {string[]} */
 	const nameIndexValueMapping = [];
-	let innerSourceIndex = -2;
+	let outerSourceIndex = -2;
 	/** @type {number[]} */
 	const innerSourceIndexMapping = [];
 	/** @type {[string | null, string | undefined][]} */
@@ -101,7 +101,7 @@ const streamChunksOfCombinedSourceMap = (
 			nameIndex,
 		) => {
 			// Check if this is a mapping to the inner source
-			if (sourceIndex === innerSourceIndex) {
+			if (sourceIndex === outerSourceIndex) {
 				// Check if there is a mapping in the inner source
 				const idx = findInnerMapping(originalLine, originalColumn);
 				if (idx !== -1) {
@@ -299,7 +299,7 @@ const streamChunksOfCombinedSourceMap = (
 		},
 		(i, source, sourceContent) => {
 			if (source === innerSourceName) {
-				innerSourceIndex = i;
+				outerSourceIndex = i;
 				if (innerSource !== undefined) sourceContent = innerSource;
 				else innerSource = /** @type {string} */ (sourceContent);
 				sourceIndexMapping[i] = -2;
diff --git a/test/ConcatSource.js b/test/ConcatSource.js
index dcf8233..f3a4df1 100644
--- a/test/ConcatSource.js
+++ b/test/ConcatSource.js
@@ -5,6 +5,7 @@ jest.mock("./__mocks__/createMappingsSerializer");
 const { ConcatSource } = require("../");
 const { RawSource } = require("../");
 const { OriginalSource } = require("../");
+const { SourceMapSource } = require("../");
 const { withReadableMappings } = require("./helpers");
 
 describe("concatSource", () => {
@@ -210,4 +211,41 @@ describe("concatSource", () => {
 		}
 	`);
 	});
+
+	it("should handle column mapping correctly with missing sources", () => {
+		const source = new ConcatSource(
+			"/*! For license information please see main.js.LICENSE.txt */",
+		);
+		const innerSource = "ab\nc";
+		const innerMap = {
+			names: [],
+			file: "x",
+			version: 3,
+			sources: ["main.js"],
+			sourcesContent: ["a\nc"],
+			mappings: "AAAA,CCAA;ADCA",
+			// ______________↑ The column mapping (CCAA) references one missing source
+		};
+		source.add(new SourceMapSource(innerSource, "main.js", innerMap));
+		const expected = {
+			source:
+				"/*! For license information please see main.js.LICENSE.txt */ab\nc",
+			map: {
+				version: 3,
+				file: "x",
+				mappings: "6DAAA,C;AACA",
+				sources: ["main.js"],
+				sourcesContent: ["a\nc"],
+				names: [],
+			},
+		};
+		expect(
+			source.sourceAndMap({
+				columns: true,
+			}),
+		).toEqual({
+			source: expected.source,
+			map: expected.map,
+		});
+	});
 });