Weird Error With Specular Shader

There seems to be a problem with this line of code:
float3 specularReflection = max(0.0, dot(normalDirection, lightDirection) ) * pow(max(0.0, dot(reflect(-lightDirection, normalDirection), viewDirection)), _Shininess );

Where I get this result :

I have figured out the problem is there when I power with “_Shininess”. If i take it out it goes back to normal.
I want to know how I can fix this.

I had a similar issue. Turned out that it was quite silly.
I noticed I had written “uniform float4 _Shininess=10;”
It’s supposed to be just a regular float