Index: flang/docs/Extensions.md
===================================================================
--- flang/docs/Extensions.md
+++ flang/docs/Extensions.md
@@ -83,13 +83,14 @@
 * `$` and `@` as legal characters in names
 * Initialization in type declaration statements using `/values/`
 * Kind specification with `*`, e.g. `REAL*4`
-* `DOUBLE COMPLEX`
+* `DOUBLE COMPLEX` as a synonym for `COMPLEX(KIND(0.D0))` --
+  but not when spelled `TYPE(DOUBLECOMPLEX)`.
 * Signed complex literal constants
 * DEC `STRUCTURE`, `RECORD`, with '%FILL'; but `UNION`, and `MAP`
   are not yet supported throughout compilation, and elicit a
   "not yet implemented" message.
 * Structure field access with `.field`
-* `BYTE` as synonym for `INTEGER(KIND=1)`
+* `BYTE` as synonym for `INTEGER(KIND=1)`; but not when spelled `TYPE(BYTE)`.
 * Quad precision REAL literals with `Q`
 * `X` prefix/suffix as synonym for `Z` on hexadecimal literals
 * `B`, `O`, `Z`, and `X` accepted as suffixes as well as prefixes
Index: flang/lib/Parser/Fortran-parsers.cpp
===================================================================
--- flang/lib/Parser/Fortran-parsers.cpp
+++ flang/lib/Parser/Fortran-parsers.cpp
@@ -168,10 +168,13 @@
 // for TYPE (...), rather than putting the alternatives within it, which
 // would fail on "TYPE(real_derived)" with a misrecognition of "real" as an
 // intrinsic-type-spec.
+// N.B. TYPE(x) is a derived type if x is a one-word extension intrinsic
+// type (BYTE or DOUBLECOMPLEX), not the extension intrinsic type.
 TYPE_CONTEXT_PARSER("declaration type spec"_en_US,
     construct<DeclarationTypeSpec>(intrinsicTypeSpec) ||
         "TYPE" >>
-            (parenthesized(construct<DeclarationTypeSpec>(intrinsicTypeSpec)) ||
+            (parenthesized(construct<DeclarationTypeSpec>(
+                 !"DOUBLECOMPLEX"_tok >> !"BYTE"_tok >> intrinsicTypeSpec)) ||
                 parenthesized(construct<DeclarationTypeSpec>(
                     construct<DeclarationTypeSpec::Type>(derivedTypeSpec))) ||
                 construct<DeclarationTypeSpec>(
@@ -209,7 +212,7 @@
             "LOGICAL" >> maybe(kindSelector))),
         extension<LanguageFeature::DoubleComplex>(
             "nonstandard usage: DOUBLE COMPLEX"_port_en_US,
-            construct<IntrinsicTypeSpec>("DOUBLE COMPLEX" >>
+            construct<IntrinsicTypeSpec>("DOUBLE COMPLEX"_sptok >>
                 construct<IntrinsicTypeSpec::DoubleComplex>())),
         extension<LanguageFeature::Byte>("nonstandard usage: BYTE"_port_en_US,
             construct<IntrinsicTypeSpec>(construct<IntegerTypeSpec>(