Index: flang/docs/Extensions.md
===================================================================
--- flang/docs/Extensions.md
+++ flang/docs/Extensions.md
@@ -266,6 +266,9 @@
   enforce it and the constraint is not necessary for a correct
   implementation.
 * A label may follow a semicolon in fixed form source.
+* A scalar logical dummy argument to a `BIND(C)` procedure does
+  not have to have `KIND=C_BOOL` since it can be converted to/from
+  `_Bool` without loss of information.
 
 ### Extensions supported when enabled by options
 
Index: flang/lib/Semantics/check-declarations.cpp
===================================================================
--- flang/lib/Semantics/check-declarations.cpp
+++ flang/lib/Semantics/check-declarations.cpp
@@ -2269,7 +2269,8 @@
           "A variable with BIND(C) attribute may only appear in the specification part of a module"_err_en_US);
       context_.SetError(symbol);
     }
-    if (auto shape{evaluate::GetShape(foldingContext_, symbol)}) {
+    auto shape{evaluate::GetShape(foldingContext_, symbol)};
+    if (shape) {
       if (evaluate::GetRank(*shape) == 0) { // 18.3.4
         if (isExplicitBindC && IsAllocatableOrPointer(symbol)) {
           messages_.Say(symbol.name(),
@@ -2310,6 +2311,13 @@
         // ok; F'2018 18.3.6 p2(6)
       } else if (derived || IsInteroperableIntrinsicType(*type)) {
         // F'2018 18.3.6 p2(4,5)
+      } else if (type->category() == DeclTypeSpec::Logical && IsDummy(symbol) &&
+          evaluate::GetRank(*shape) == 0) {
+        // Special exception: LOGICAL scalar dummy arguments can be converted
+        // before a call -- & after if not INTENT(IN) -- without loss of
+        // information, and are accepted by some older compilers.
+        messages_.Say(symbol.name(),
+            "A BIND(C) LOGICAL dummy argument should have the interoperable KIND=C_BOOL"_port_en_US);
       } else if (symbol.attrs().test(Attr::VALUE)) {
         messages_.Say(symbol.name(),
             "A BIND(C) VALUE dummy argument must have an interoperable type"_err_en_US);
Index: flang/test/Semantics/bind-c11.f90
===================================================================
--- flang/test/Semantics/bind-c11.f90
+++ flang/test/Semantics/bind-c11.f90
@@ -8,7 +8,7 @@
   real, allocatable, bind(c) :: x3(:)
  contains
   subroutine s1(x) bind(c)
-    !ERROR: A BIND(C) VALUE dummy argument must have an interoperable type
+    !PORTABILITY: A BIND(C) LOGICAL dummy argument should have the interoperable KIND=C_BOOL
     logical(2), intent(in), value :: x
   end
   subroutine s2(x) bind(c)