diff --git a/reference/shaders-msl/vert/basic.vert b/reference/shaders-msl/vert/basic.vert
index b895e104..d2c96d2c 100644
--- a/reference/shaders-msl/vert/basic.vert
+++ b/reference/shaders-msl/vert/basic.vert
@@ -10,8 +10,8 @@ struct UBO
 
 struct main0_in
 {
+    float3 aNormal [[attribute(1)]];
     float4 aVertex [[attribute(0)]];
-    float3 aNormal [[attribute(0)]];
 };
 
 struct main0_out
diff --git a/shaders-msl/vert/basic.vert b/shaders-msl/vert/basic.vert
index 801724f3..6d8bdc17 100644
--- a/shaders-msl/vert/basic.vert
+++ b/shaders-msl/vert/basic.vert
@@ -4,8 +4,10 @@ layout(std140) uniform UBO
 {
     uniform mat4 uMVP;
 };
-in vec4 aVertex;
-in vec3 aNormal;
+
+layout(location = 0) in vec4 aVertex;
+layout(location = 1) in vec3 aNormal;
+
 out vec3 vNormal;
 
 void main()
diff --git a/test_shaders.py b/test_shaders.py
index 1ad768e9..bfea9f1c 100755
--- a/test_shaders.py
+++ b/test_shaders.py
@@ -2,6 +2,7 @@
 
 import sys
 import os
+import os.path
 import subprocess
 import tempfile
 import re
@@ -10,6 +11,8 @@ import hashlib
 import shutil
 import argparse
 
+METALC = '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/usr/bin/metal'
+
 def parse_stats(stats):
     m = re.search('([0-9]+) work registers', stats)
     registers = int(m.group(1)) if m else 0
@@ -60,11 +63,8 @@ def get_shader_stats(shader):
     returned = stdout.decode('utf-8')
     return parse_stats(returned)
 
-def validate_shader(shader, vulkan):
-    if vulkan:
-        subprocess.check_call(['glslangValidator', '-V', shader])
-    else:
-        subprocess.check_call(['glslangValidator', shader])
+def validate_shader_msl(shader):
+    subprocess.check_call([METALC, '-x', 'metal', '-std=ios-metal1.0', '-Werror', shader])
 
 def cross_compile_msl(shader):
     spirv_f, spirv_path = tempfile.mkstemp()
@@ -76,7 +76,9 @@ def cross_compile_msl(shader):
     subprocess.check_call([spirv_cross_path, '--entry', 'main', '--output', msl_path, spirv_path, '--metal'])
     subprocess.check_call(['spirv-val', spirv_path])
 
-    # TODO: Add optional validation of the MSL output.
+    if os.path.exists(METALC):
+        validate_shader_msl(msl_path)
+
     return (spirv_path, msl_path)
 
 def cross_compile_hlsl(shader):
@@ -92,6 +94,12 @@ def cross_compile_hlsl(shader):
     # TODO: Add optional validation of the HLSL output.
     return (spirv_path, msl_path)
 
+def validate_shader(shader, vulkan):
+    if vulkan:
+        subprocess.check_call(['glslangValidator', '-V', shader])
+    else:
+        subprocess.check_call(['glslangValidator', shader])
+
 def cross_compile(shader, vulkan, spirv, invalid_spirv, eliminate, is_legacy, flatten_ubo):
     spirv_f, spirv_path = tempfile.mkstemp()
     glsl_f, glsl_path = tempfile.mkstemp(suffix = os.path.basename(shader))
@@ -297,6 +305,9 @@ def main():
         sys.stderr.write('Need shader folder.\n')
         sys.exit(1)
 
+    if os.path.exists(METALC):
+        subprocess.check_call([METALC, '--version'])
+
     test_shaders(args.folder, args.update, args.malisc, args.keep, 'metal' if args.metal else ('hlsl' if args.hlsl else 'glsl'))
     if args.malisc:
         print('Stats in stats.csv!')