diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -46,6 +46,9 @@
     }
   }
   if (const auto *expr{arg.UnwrapExpr()}) {
+    if (std::holds_alternative<evaluate::BOZLiteralConstant>(expr->u)) {
+      messages.Say("BOZ argument requires an explicit interface"_err_en_US);
+    }
     if (auto named{evaluate::ExtractNamedEntity(*expr)}) {
       const Symbol &symbol{named->GetLastSymbol()};
       if (symbol.Corank() > 0) {
diff --git a/flang/test/Semantics/boz-literal-constants.f90 b/flang/test/Semantics/boz-literal-constants.f90
--- a/flang/test/Semantics/boz-literal-constants.f90
+++ b/flang/test/Semantics/boz-literal-constants.f90
@@ -77,4 +77,7 @@
   res = MERGE_BITS(B"1101",3,B"1011")
 
   res = REAL(B"1101")
+
+  !ERROR: BOZ argument requires an explicit interface
+  call implictSub(Z'12345')
 end subroutine