diff --git a/lib/src/cellar/SourceFetcher.scala b/lib/src/cellar/SourceFetcher.scala
index 9162a16..60308c5 100644
--- a/lib/src/cellar/SourceFetcher.scala
+++ b/lib/src/cellar/SourceFetcher.scala
@@ -1,8 +1,9 @@
 package cellar
 
-import cats.effect.IO
+import cats.effect.{IO, Resource}
 import coursierapi.Repository
 import fs2.io.file.Path
+import fs2.io.readInputStream
 
 import java.util.zip.ZipFile
 import scala.jdk.CollectionConverters.*
@@ -21,7 +22,7 @@ object SourceFetcher:
       case None =>
         IO.pure(Left(s"No sources JAR published for '${coord.render}'."))
       case Some(jar) =>
-        IO.blocking(extractLines(jar, sourceFilePath, startLine, endLine))
+        extractLines(jar, sourceFilePath, startLine, endLine)
     }
 
   private def extractLines(
@@ -29,20 +30,26 @@ object SourceFetcher:
       sourceFilePath: String,
       startLine: Int,
       endLine: Int
-  ): Either[String, SourceResult] =
+  ): IO[Either[String, SourceResult]] =
     val normalizedSource = sourceFilePath.replace('\\', '/')
-    val zip = ZipFile(jar.toNioPath.toFile)
-    try
-      val entry = zip.entries().asScala.find { e =>
-        !e.isDirectory && normalizedSource.endsWith(e.getName)
-      }
-      entry match
+    Resource.fromAutoCloseable(IO.blocking(ZipFile(jar.toNioPath.toFile))).use { zip =>
+      IO.blocking {
+        zip.entries().asScala
+          .find(e => !e.isDirectory && normalizedSource.endsWith(e.getName))
+          .map(e => (e.getName, zip.getInputStream(e)))
+      }.flatMap {
         case None =>
-          Left(s"Source file not found in JAR (looked for suffix of '$normalizedSource').")
-        case Some(e) =>
-          val allLines = scala.io.Source.fromInputStream(zip.getInputStream(e), "UTF-8")
-            .getLines().toIndexedSeq
-          val extracted = allLines.slice(startLine, endLine + 1)
-          Right(SourceResult(e.getName, startLine, endLine, extracted))
-    finally
-      zip.close()
+          IO.pure(Left(s"Source file not found in JAR (looked for suffix of '$normalizedSource')."))
+        case Some((name, is)) =>
+          readInputStream(IO.pure(is), chunkSize = 65536)
+            .through(fs2.text.utf8.decode)
+            .through(fs2.text.lines)
+            .compile
+            .toVector
+            .map { allLines =>
+              val extracted = if endLine == Int.MaxValue then allLines.drop(startLine)
+                              else allLines.slice(startLine, endLine + 1)
+              Right(SourceResult(name, startLine, endLine, extracted))
+            }
+      }
+    }
diff --git a/lib/test/src/cellar/IntegrationTest.scala b/lib/test/src/cellar/IntegrationTest.scala
index 42de821..84a8ab4 100644
--- a/lib/test/src/cellar/IntegrationTest.scala
+++ b/lib/test/src/cellar/IntegrationTest.scala
@@ -218,7 +218,7 @@ class IntegrationTest extends CatsEffectSuite:
         )
       }
 
-  test("get-source: Java class returns java code block"):
+  test("get-source: Java class returns java code block with source body"):
     TestFixtures.assumeFixturesAvailable()
     val console = CapturingConsole()
     given Console[IO] = console
@@ -230,7 +230,9 @@ class IntegrationTest extends CatsEffectSuite:
       )
       .map { code =>
         assertEquals(code, ExitCode.Success)
-        assert(console.outBuf.toString.contains("```java"), s"Output: ${console.outBuf}")
+        val out = console.outBuf.toString
+        assert(out.contains("```java"), s"Output: $out")
+        assert(out.contains("getDefault"), s"Expected source body in: $out")
       }
 
   test("get-source: trait with same-file companion returns both"):