diff --git a/flang/lib/Parser/prescan.cpp b/flang/lib/Parser/prescan.cpp
--- a/flang/lib/Parser/prescan.cpp
+++ b/flang/lib/Parser/prescan.cpp
@@ -144,6 +144,10 @@
   case LineClassification::Kind::Source:
     BeginStatementAndAdvance();
     if (inFixedForm_) {
+      if (features_.IsEnabled(LanguageFeature::OldDebugLines) &&
+          (*at_ == 'D' || *at_ == 'd')) {
+        NextChar();
+      }
       LabelField(tokens);
     } else if (skipLeadingAmpersand_) {
       skipLeadingAmpersand_ = false;