diff --git a/gcc/fortran/interface.cc b/gcc/fortran/interface.cc
index 8c4571e0aa6..ba7fb5dfea5 100644
--- a/gcc/fortran/interface.cc
+++ b/gcc/fortran/interface.cc
@@ -4616,6 +4616,35 @@ build_compcall_for_operator (gfc_expr* e, gfc_actual_arglist* actual,
 }
 
 
+/* Check if the type of an actual argument is OK to use with an
+   unlimited polymorphic formal argument in a defined operation.  */
+
+static bool
+upoly_ok (bt type, gfc_intrinsic_op op)
+{
+  bool ok = false;
+  if (type == BT_DERIVED || type == BT_CLASS)
+    ok = true;
+  else if ((op >= INTRINSIC_UPLUS && op <= INTRINSIC_POWER)
+	   && (type == BT_LOGICAL || type == BT_CHARACTER))
+    ok = true;
+  else if ((op == INTRINSIC_CONCAT) && (type != BT_CHARACTER))
+    ok = true;
+  else if ((op >= INTRINSIC_GT && op <= INTRINSIC_LE)
+	   && (type == BT_COMPLEX))
+    ok = true;
+  else if ((op >= INTRINSIC_GT_OS) && (op <= INTRINSIC_LE_OS)
+	   && (type == BT_COMPLEX))
+    ok = true;
+  else if ((op >= INTRINSIC_AND) && (op <= INTRINSIC_NEQV)
+	   && (type != BT_LOGICAL))
+    ok = true;
+  else if ((op == INTRINSIC_NOT) && (type != BT_LOGICAL))
+    ok = true;
+  return ok;
+}
+
+
 /* This subroutine is called when an expression is being resolved.
    The expression node in question is either a user defined operator
    or an intrinsic operator with arguments that aren't compatible
@@ -4737,6 +4766,24 @@ gfc_extend_expr (gfc_expr *e)
 	  if (sym != NULL)
 	    break;
 	}
+
+      /* F2018(15.4.3.4.2): "If the operator is an intrinsic-operator (R608),
+	 the number of dummy arguments shall be consistent with the intrinsic
+	 uses of that operator, and the types, kind type parameters, or ranks
+	 of the dummy arguments shall differ from those required for the
+	 intrinsic operation (10.1.5)." ie. the use of unlimited polymorphic
+	 formal arguments must not override the intrinsic uses.  */
+      if (sym && (UNLIMITED_POLY (sym->formal->sym)
+		  || (sym->formal->next
+		      && UNLIMITED_POLY (sym->formal->next->sym))))
+	{
+	  bool arg2 = (actual->next != NULL);
+	  bool a1ok = upoly_ok (actual->expr->ts.type, e->value.op.op);
+	  bool a2ok = arg2 && upoly_ok (actual->next->expr->ts.type,
+					e->value.op.op);
+	  if ((!arg2 && !a1ok) || (arg2 && (!a1ok && !a2ok)))
+	    sym = NULL;
+	}
     }
 
   /* TODO: Do an ambiguity-check and error if multiple matching interfaces are