When parsing a YAML file with yaml-cpp, getting an undefined node type

Question

I'm testing out YAML to see if it would be a good fit for a data storage format for a game engine. I've created this sample YAML file:

---
ShaderProperties:
    EntryPoint                      : UnlitHomogenousVS
    Profile                         : vs_4_0
    Model                           : HLSL_4
    Uniforms:
        - name                      : gTint
          type                      : kShaderUniformTypeFloat4
          defaultValue              : 1.0f, 1.0f, 1.0f, 1.0f
          constantBuffer            : cbObjectProperties
          constantBufferOffset      : 0
          usage                     : Property
    Samplers:
    ConstantBuffers:
        - name                      : cbObjectProperties
          register                  : 2
          size                      : 16
          type                      : kShaderTypeVertex
    Attributes:
        - name                      : position
          type                      : kShaderAttributeTypeFloat4
          usage                     : kShaderAttributeUsagePosition
        - name                      : color
          type                      : kShaderAttributeTypeFloat4
          usage                     : kShaderAttributeUsageColor0
ShaderText:  >
    //--
    // UnlitHomogenous.vs
    //
    // This vertex shader will color geometry with only a homogenous transform.
    //--

    //--
    // VertexInput
    //--
    struct VertexInput
    {
        float4 position : POSITION;
        float4 color    : COLOR;
    };

    //--
    // VertexOutput
    //--
    struct VertexOutput
    {
        float4 position : SV_POSITION;
        float4 color    : COLOR;
    };

    //--
    // Global Variables
    //--

    cbuffer cbObjectProperties : register(b2)
    {
        float4 gTint = float4( 1.0f, 1.0f, 1.0f, 1.0f );
    };

    //--
    // Main Function
    //--
    VertexOutput UnlitHomogenousVS( VertexInput input )
    {
        VertexOutput output = (VertexOutput)0;

        output.position = input.position * gTint;
        output.color = input.color;

        return output;
    }
...

Now, this file loads and seems to parse fine, but when I try to read in the node "EntryPoint" I get a valid node returned, but with an undefined node type, where I was expecting a scalar.

Here is the code that I'm using to read in the node.

YAML::Node root = YAML::LoadFile( filepathString );

if( root.IsNull() )
{
    return Failure_FileNotFound;
}

YAML::Node shaderProperties = root[ "ShaderProperties" ];
if( shaderProperties.IsNull() )
{
    return Failure_MalformedData;
}

YAML::Node& entryPointNode = shaderProperties[ "EntryPoint" ];
if( entryPointNode.IsNull() || !entryPointNode.IsDefined() )
{
    TC_SHADER_IMPORTER_LOG_ERROR( TCString( "Failed to parse shader: ") + mCurrentName + TCString( ", no entry point was found" ) );
    return Failure_MalformedData;
}
output->mEntryPointName = entryPointNode.as<std::string>().c_str();

Is there anything obvious that I'm missing? I am able to successfully load this file, so I assume that the YAML is valid. If I take out the check for IsDefined() and just try to cast the node to a string, I get a bad conversion.

Thanks for any and all help!

EDIT:

The issue was that I was using \t tabs between the tag name, (EntryPoint), and the colon instead of ' 's to tab.