diff --git a/flang/include/flang/Common/format.h b/flang/include/flang/Common/format.h
--- a/flang/include/flang/Common/format.h
+++ b/flang/include/flang/Common/format.h
@@ -471,7 +471,7 @@
     NextToken();
     return true;
   }
-  if (*argString_ != 'A') {
+  if (*argString_ != 'A' && *argString_ != 'L') {
     ReportWarning("Expected '%s' edit descriptor 'w' value"); // C1306
   }
   return false;
diff --git a/flang/lib/Parser/io-parsers.cpp b/flang/lib/Parser/io-parsers.cpp
--- a/flang/lib/Parser/io-parsers.cpp
+++ b/flang/lib/Parser/io-parsers.cpp
@@ -601,28 +601,26 @@
         "A " >> pure(format::IntrinsicTypeDataEditDesc::Kind::A), maybe(width),
         noInt, noInt) ||
     // PGI/Intel extension: omitting width (and all else that follows)
-    extension<LanguageFeature::AbbreviatedEditDescriptor>(
-        "nonstandard usage: abbreviated edit descriptor"_port_en_US,
-        construct<format::IntrinsicTypeDataEditDesc>(
-            "I " >> pure(format::IntrinsicTypeDataEditDesc::Kind::I) ||
-                ("B "_tok / !letter /* don't occlude BN & BZ */) >>
-                    pure(format::IntrinsicTypeDataEditDesc::Kind::B) ||
-                "O " >> pure(format::IntrinsicTypeDataEditDesc::Kind::O) ||
-                "Z " >> pure(format::IntrinsicTypeDataEditDesc::Kind::Z) ||
-                "F " >> pure(format::IntrinsicTypeDataEditDesc::Kind::F) ||
-                ("D "_tok / !letter /* don't occlude DT, DC, & DP */) >>
-                    pure(format::IntrinsicTypeDataEditDesc::Kind::D) ||
-                "E " >>
-                    ("N " >>
-                            pure(format::IntrinsicTypeDataEditDesc::Kind::EN) ||
-                        "S " >>
-                            pure(format::IntrinsicTypeDataEditDesc::Kind::ES) ||
-                        "X " >>
-                            pure(format::IntrinsicTypeDataEditDesc::Kind::EX) ||
-                        pure(format::IntrinsicTypeDataEditDesc::Kind::E)) ||
-                "G " >> pure(format::IntrinsicTypeDataEditDesc::Kind::G) ||
-                "L " >> pure(format::IntrinsicTypeDataEditDesc::Kind::L),
-            noInt, noInt, noInt)))
+    // Parse them just to get them to the I/O checker in semantics;
+    // they are not supported by the runtime.
+    extension<LanguageFeature::AbbreviatedEditDescriptor>(construct<
+        format::IntrinsicTypeDataEditDesc>(
+        "I " >> pure(format::IntrinsicTypeDataEditDesc::Kind::I) ||
+            ("B "_tok / !letter /* don't occlude BN & BZ */) >>
+                pure(format::IntrinsicTypeDataEditDesc::Kind::B) ||
+            "O " >> pure(format::IntrinsicTypeDataEditDesc::Kind::O) ||
+            "Z " >> pure(format::IntrinsicTypeDataEditDesc::Kind::Z) ||
+            "F " >> pure(format::IntrinsicTypeDataEditDesc::Kind::F) ||
+            ("D "_tok / !letter /* don't occlude DT, DC, & DP */) >>
+                pure(format::IntrinsicTypeDataEditDesc::Kind::D) ||
+            "E " >>
+                ("N " >> pure(format::IntrinsicTypeDataEditDesc::Kind::EN) ||
+                    "S " >> pure(format::IntrinsicTypeDataEditDesc::Kind::ES) ||
+                    "X " >> pure(format::IntrinsicTypeDataEditDesc::Kind::EX) ||
+                    pure(format::IntrinsicTypeDataEditDesc::Kind::E)) ||
+            "G " >> pure(format::IntrinsicTypeDataEditDesc::Kind::G) ||
+            "L " >> pure(format::IntrinsicTypeDataEditDesc::Kind::L),
+        noInt, noInt, noInt)))
 
 // R1307 data-edit-desc (part 2 of 2)
 // R1312 v -> [sign] digit-string