diff --git a/lib/internal/errors/error_source.js b/lib/internal/errors/error_source.js
index eddd6af230801b..c17f5a151c7014 100644
--- a/lib/internal/errors/error_source.js
+++ b/lib/internal/errors/error_source.js
@@ -32,6 +32,10 @@ function getErrorSourceLocation(error) {
     startColumn,
   } = pos;
 
+  if (!sourceLine) {
+    return;
+  }
+
   // Source map is not enabled. Return the source line directly.
   if (!getSourceMapsSupport().enabled) {
     return { sourceLine, startColumn };
@@ -39,7 +43,8 @@ function getErrorSourceLocation(error) {
 
   const sm = findSourceMap(scriptResourceName);
   if (sm === undefined) {
-    return;
+    // No source map for this file; use the generated source line.
+    return { sourceLine, startColumn };
   }
   const {
     originalLine,
@@ -49,7 +54,9 @@ function getErrorSourceLocation(error) {
   const originalSourceLine = getSourceLine(sm, originalSource, originalLine, originalColumn);
 
   if (!originalSourceLine) {
-    return;
+    // Source map exists but original source is unavailable; use the
+    // generated source line rather than returning undefined.
+    return { sourceLine, startColumn };
   }
 
   return {
diff --git a/test/fixtures/source-map/output/source_map_assert_no_source_map.mjs b/test/fixtures/source-map/output/source_map_assert_no_source_map.mjs
new file mode 100644
index 00000000000000..d6035109d56db8
--- /dev/null
+++ b/test/fixtures/source-map/output/source_map_assert_no_source_map.mjs
@@ -0,0 +1,9 @@
+// Flags: --enable-source-maps
+
+import '../../../common/index.mjs';
+import { strict as assert } from 'node:assert';
+
+// Regression test for https://github.com/nodejs/node/issues/63169
+// Under --enable-source-maps with no source map for this file, a failing
+// assert(value) must throw AssertionError, not TypeError ERR_INVALID_ARG_TYPE.
+assert(false);
diff --git a/test/fixtures/source-map/output/source_map_assert_no_source_map.snapshot b/test/fixtures/source-map/output/source_map_assert_no_source_map.snapshot
new file mode 100644
index 00000000000000..0a2ea1a45fe6f3
--- /dev/null
+++ b/test/fixtures/source-map/output/source_map_assert_no_source_map.snapshot
@@ -0,0 +1,20 @@
+node:internal/modules/run_main:<line>
+    triggerUncaughtException(
+    ^
+
+AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:
+
+  assert(false)
+
+    at file://<project-root>/test/fixtures/source-map/output/source_map_assert_no_source_map.mjs:9:1
+    at <node-internal-frames>
+    at <node-internal-frames> {
+  generatedMessage: true,
+  code: 'ERR_ASSERTION',
+  actual: false,
+  expected: true,
+  operator: '==',
+  diff: 'simple'
+}
+
+Node.js <node-version>
diff --git a/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.cjs b/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.cjs
new file mode 100644
index 00000000000000..21f2ec8965fb05
--- /dev/null
+++ b/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.cjs
@@ -0,0 +1,10 @@
+// Flags: --enable-source-maps
+
+'use strict';
+require('../../../common');
+const assert = require('node:assert');
+
+// Regression test for https://github.com/nodejs/node/issues/63169
+// Under --enable-source-maps with no source map for this file, a failing
+// assert.ok(value) must throw AssertionError, not TypeError ERR_INVALID_ARG_TYPE.
+assert.ok(false);
diff --git a/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.snapshot b/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.snapshot
new file mode 100644
index 00000000000000..8ee5ff2ee29498
--- /dev/null
+++ b/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.snapshot
@@ -0,0 +1,20 @@
+node:internal/assert/utils:<line>
+  throw error;
+  ^
+
+AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:
+
+  assert.ok(false)
+
+    at Object.<anonymous> (<project-root>/test/fixtures/source-map/output/source_map_assert_ok_no_source_map.cjs:10:8)
+    at <node-internal-frames>
+    at <node-internal-frames> {
+  generatedMessage: true,
+  code: 'ERR_ASSERTION',
+  actual: false,
+  expected: true,
+  operator: '==',
+  diff: 'simple'
+}
+
+Node.js <node-version>
diff --git a/test/parallel/test-node-output-sourcemaps.mjs b/test/parallel/test-node-output-sourcemaps.mjs
index 26baa0cd53afed..c96eac2bd0310c 100644
--- a/test/parallel/test-node-output-sourcemaps.mjs
+++ b/test/parallel/test-node-output-sourcemaps.mjs
@@ -5,6 +5,8 @@ import { describe, it } from 'node:test';
 
 describe('sourcemaps output', { concurrency: !process.env.TEST_PARALLEL }, () => {
   const tests = [
+    { name: 'source-map/output/source_map_assert_no_source_map.mjs' },
+    { name: 'source-map/output/source_map_assert_ok_no_source_map.cjs' },
     { name: 'source-map/output/source_map_disabled_by_api.js' },
     { name: 'source-map/output/source_map_disabled_by_process_api.js' },
     { name: 'source-map/output/source_map_enabled_by_api.js' },