diff --git a/flang/test/Driver/emit-asm-from-mlir.mlir b/flang/test/Driver/emit-asm-from-mlir.mlir
--- a/flang/test/Driver/emit-asm-from-mlir.mlir
+++ b/flang/test/Driver/emit-asm-from-mlir.mlir
@@ -1,10 +1,9 @@
-; Verify that the driver can consume MLIR/FIR files.
+// Verify that the driver can consume MLIR/FIR files.
 
-; RUN: %flang_fc1 -S %s -o - | FileCheck %s
-
-; CHECK-LABEL: foo:
-; CHECK: ret
+// RUN: %flang_fc1 -S %s -o - | FileCheck %s
 
+// CHECK-LABEL: foo:
+// CHECK: ret
 func.func @foo() {
   return
 }
diff --git a/flang/test/lit.cfg.py b/flang/test/lit.cfg.py
--- a/flang/test/lit.cfg.py
+++ b/flang/test/lit.cfg.py
@@ -27,8 +27,8 @@
 # suffixes: A list of file extensions to treat as test files.
 config.suffixes = ['.c', '.cpp', '.f', '.F', '.ff', '.FOR', '.for', '.f77', '.f90', '.F90',
                    '.ff90', '.f95', '.F95', '.ff95', '.fpp', '.FPP', '.cuf'
-                   '.CUF', '.f18', '.F18', '.fir', '.f03', '.F03', '.f08',
-                   '.F08', '.ll']
+                   '.CUF', '.f18', '.F18', '.f03', '.F03', '.f08', '.F08',
+                   '.ll', '.fir', '.mlir']
 
 config.substitutions.append(('%PATH%', config.environment['PATH']))
 config.substitutions.append(('%llvmshlibdir', config.llvm_shlib_dir))