diff --git a/test/lex/backslash.f90 b/test/lex/backslash.f90
index bcdb556faf4..cb21928b346 100644
--- a/test/lex/backslash.f90
+++ b/test/lex/backslash.f90
@@ -8,6 +8,10 @@
 ! RUN: %flang -c -fno-backslash %s
 ! RUN: not %flang -c -Mnobackslash %s 2>&1 | FileCheck %s
 ! RUN: not %flang -c -fbackslash %s 2>&1 | FileCheck %s
+! RUN: %flang -c -Mnobackslash -Mbackslash %s
+! RUN: %flang -c -fbackslash -fno-backslash %s
+! RUN: not %flang -c -Mnobackslash -Mbackslash -Mnobackslash %s 2>&1 | FileCheck %s
+! RUN: not %flang -c -fno-backslash -fbackslash %s 2>&1 | FileCheck %s
 
 write (*,*) "\" ! CHECK: Unmatched quote
 end