diff --git a/flang/lib/Parser/source.cpp b/flang/lib/Parser/source.cpp
--- a/flang/lib/Parser/source.cpp
+++ b/flang/lib/Parser/source.cpp
@@ -133,6 +133,18 @@
     buf_->getBuffer()[0] = '\n';
   }
   buf_end_ = RemoveCarriageReturns(buf_->getBuffer());
+  if (content().back() != '\n') {
+    // Don't bother to copy if we have spare memory
+    if (content().size() >= buf_->getBufferSize()) {
+      auto tmp_buf = llvm::WritableMemoryBuffer::getNewUninitMemBuffer(
+          content().size() + 1);
+      llvm::copy(content(), tmp_buf->getBufferStart());
+      Close();
+      buf_ = std::move(tmp_buf);
+    }
+    buf_end_++;
+    buf_->getBuffer()[buf_end_ - 1] = '\n';
+  }
   IdentifyPayload();
   RecordLineStarts();
 }