diff --git a/__tests__/fixtures/tsconfigs/includes/a.d.ts b/__tests__/fixtures/tsconfigs copy/includes/a.d.ts
similarity index 100%
rename from __tests__/fixtures/tsconfigs/includes/a.d.ts
rename to __tests__/fixtures/tsconfigs copy/includes/a.d.ts
diff --git a/__tests__/fixtures/tsconfigs/project/a.ts b/__tests__/fixtures/tsconfigs copy/project/a.ts
similarity index 100%
rename from __tests__/fixtures/tsconfigs/project/a.ts
rename to __tests__/fixtures/tsconfigs copy/project/a.ts
diff --git a/__tests__/fixtures/tsconfigs/project/nested/b.ts b/__tests__/fixtures/tsconfigs copy/project/extends/d.ts
similarity index 100%
rename from __tests__/fixtures/tsconfigs/project/nested/b.ts
rename to __tests__/fixtures/tsconfigs copy/project/extends/d.ts
diff --git a/__tests__/fixtures/tsconfigs copy/project/extends/tsconfig.json b/__tests__/fixtures/tsconfigs copy/project/extends/tsconfig.json
new file mode 100644
index 0000000..a8df22f
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs copy/project/extends/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "extends": "../tsconfig.json"
+}
\ No newline at end of file
diff --git a/__tests__/fixtures/tsconfigs copy/project/glob/c.ts b/__tests__/fixtures/tsconfigs copy/project/glob/c.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs copy/project/glob/tsconfig.json b/__tests__/fixtures/tsconfigs copy/project/glob/tsconfig.json
new file mode 100644
index 0000000..8d8c51c
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs copy/project/glob/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "include": ["../../includes/*.*", "./**/*.*"]
+}
\ No newline at end of file
diff --git a/__tests__/fixtures/tsconfigs copy/project/nested/b.ts b/__tests__/fixtures/tsconfigs copy/project/nested/b.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs copy/project/tsconfig.json b/__tests__/fixtures/tsconfigs copy/project/tsconfig.json
new file mode 100644
index 0000000..441ca22
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs copy/project/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "include": ["../includes/a.d.ts"]
+}
diff --git a/__tests__/fixtures/tsconfigs/decls/one.d.ts b/__tests__/fixtures/tsconfigs/decls/one.d.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/decls/tsconfig.json b/__tests__/fixtures/tsconfigs/decls/tsconfig.json
new file mode 100644
index 0000000..f24f40a
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs/decls/tsconfig.json
@@ -0,0 +1,3 @@
+{
+    "include": ["./**/*.*"]
+}
\ No newline at end of file
diff --git a/__tests__/fixtures/tsconfigs/decls/two.d.ts b/__tests__/fixtures/tsconfigs/decls/two.d.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/extends/extends.ts b/__tests__/fixtures/tsconfigs/extends/extends.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/extends/tsconfig.json b/__tests__/fixtures/tsconfigs/extends/tsconfig.json
new file mode 100644
index 0000000..f84b9fd
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs/extends/tsconfig.json
@@ -0,0 +1,4 @@
+{
+    "extends": "../project/tsconfig.json",
+    "include": ["./**/*.*"]
+}
\ No newline at end of file
diff --git a/__tests__/fixtures/tsconfigs/glob/glob.ts b/__tests__/fixtures/tsconfigs/glob/glob.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/glob/tsconfig.json b/__tests__/fixtures/tsconfigs/glob/tsconfig.json
new file mode 100644
index 0000000..375f696
--- /dev/null
+++ b/__tests__/fixtures/tsconfigs/glob/tsconfig.json
@@ -0,0 +1,3 @@
+{
+    "include": ["../decls/*.d.ts", "./**/*.*"]
+}
\ No newline at end of file
diff --git a/__tests__/fixtures/tsconfigs/project/nested/nested.ts b/__tests__/fixtures/tsconfigs/project/nested/nested.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/project/project.ts b/__tests__/fixtures/tsconfigs/project/project.ts
new file mode 100644
index 0000000..e69de29
diff --git a/__tests__/fixtures/tsconfigs/project/tsconfig.json b/__tests__/fixtures/tsconfigs/project/tsconfig.json
index 441ca22..4aee49e 100644
--- a/__tests__/fixtures/tsconfigs/project/tsconfig.json
+++ b/__tests__/fixtures/tsconfigs/project/tsconfig.json
@@ -1,3 +1,3 @@
 {
-    "include": ["../includes/a.d.ts"]
+    "include": ["../decls/one.d.ts", "./**/*.*"]
 }
diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index f0822c3..2b824ed 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -508,18 +508,22 @@ describe('dependencyTree', () => {
     it('adds files in `include` from nearest tsconfig.json', async () => {
       expect.hasAssertions();
       const result = await dependencyTree.gather();
+      const decl1 = fixture('tsconfigs', 'decls', 'one.d.ts');
+      const decl2 = fixture('tsconfigs', 'decls', 'two.d.ts');
       expect(result).toStrictEqual({
         missing: new Map(),
         resolved: new Map([
+          [fixture('tsconfigs', 'project', 'project.ts'), new Set([decl1])],
           [
-            fixture('tsconfigs', 'project', 'a.ts'),
-            new Set([fixture('tsconfigs', 'includes', 'a.d.ts')]),
+            fixture('tsconfigs', 'project', 'nested', 'nested.ts'),
+            new Set([decl1]),
           ],
-          [
-            fixture('tsconfigs', 'project', 'nested', 'b.ts'),
-            new Set([fixture('tsconfigs', 'includes', 'a.d.ts')]),
-          ],
-          [fixture('tsconfigs', 'includes', 'a.d.ts'), new Set([])],
+          [fixture('tsconfigs', 'glob', 'glob.ts'), new Set([decl1, decl2])],
+          // "includes" is overwritten in the child config
+          [fixture('tsconfigs', 'extends', 'extends.ts'), new Set([])],
+          // decls in the same dir that includes './**.*.*' depend on one another
+          [fixture('tsconfigs', 'decls', 'one.d.ts'), new Set([decl2])],
+          [fixture('tsconfigs', 'decls', 'two.d.ts'), new Set([decl1])],
         ]),
       });
     });
diff --git a/src/processors/typescript.ts b/src/processors/typescript.ts
index 7ebafbd..8b93f2e 100644
--- a/src/processors/typescript.ts
+++ b/src/processors/typescript.ts
@@ -190,39 +190,36 @@ export class TypeScriptFileProcessor implements FileProcessor {
     },
   );
 
-  /**
-   * Finds the tsconfig.json that this file is included by. Does this by searching in the same directory,
-   * and then searching in each dir all the way to the root directory.
-   */
-  private includesFromNearestTsconfigFile = memoize(
-    async (file: Path): Promise<string[]> => {
-      const maybeTsconfig = await findUp('tsconfig.json', {
-        cwd: path.dirname(file),
-        stopAt: this.rootDir,
-      });
-      if (maybeTsconfig == null) {
-        return [];
-      }
-
-      const json = JSON.parse(
-        await fs.promises.readFile(maybeTsconfig, 'utf8'),
-      );
-      if (!('include' in json)) {
-        return [];
-      }
+  private async includesFromNearestTsconfigFile(file: Path): Promise<string[]> {
+    const tsconfigPath = ts.findConfigFile(
+      path.dirname(file),
+      ts.sys.fileExists,
+    );
+    if (!tsconfigPath || !tsconfigPath.startsWith(this.rootDir)) {
+      return [];
+    }
 
-      const include = json['include'] as string[];
-      const tsconfigDir = path.dirname(maybeTsconfig);
-      return (
-        include
-          // filter out globbed includes
-          // TODO: support globbed includes
-          .filter((maybeGlob) => !maybeGlob.includes('*'))
-          // make the includes absolute
-          .map((include) => path.join(tsconfigDir, include))
-      );
-    },
-  );
+    debug.enabled = true;
+    const json = ts.parseJsonText(
+      tsconfigPath,
+      await fs.promises.readFile(tsconfigPath, 'utf-8'),
+    );
+    const parsed = ts.parseJsonSourceFileConfigFileContent(
+      json,
+      ts.sys,
+      path.dirname(tsconfigPath),
+    );
+    debug(path.relative(this.rootDir, tsconfigPath));
+    debug(parsed);
+
+    return parsed.fileNames.filter(
+      (fileName) =>
+        // only include .d.ts files. all other references should be made using `import` or `require`.
+        fileName.endsWith('.d.ts') &&
+        // files do not depend on themselves
+        fileName !== file,
+    );
+  }
 
   // Finds an implicit 'import' in the entry point object literal, like:
   //