[Tex/LaTex] Using tcolorbox, the first letter in the body disappears. What can be done

Question

I'm using tcolorbox but the first letter of the body text always disappears.

\documentclass[11pt, oneside]{article}      
\usepackage[english]{babel}         
\usepackage{tcolorbox}              
\tcbuselibrary{theorems}                
\newtcbtheorem[number within=section]{myprop}{Proposition}{colback=blue!5,colframe=blue!35!black,fonttitle=\bfseries}{th}

\begin{document}
\begin{myprop}{Proposition name}
Just some text.
\end{myprop}
\end{document}

The previous code results in:

It's a fairly easy to just type the first letter twice (which yields the desired effect) but if there is a more legitimate solution I'm interested in hearing it.

Edit: Arun Debray is correct. The environment takes two arguments and should be written as \begin{myprop}{Proposition name}{label}. Problem solved!

Answer 1

Any environment defined by \newtcbtheorem takes two arguments: the proposition name and the proposition label. Since you didn't specify the label, the parser gobbles the first letter as the label. Try using \begin{myprop}{Prop. name}{prop_label}.

Source: tcolorbox documentation.