AUCTeX/LaTeX - ERROR: Undefined control sequence. documentclass

Question

I am using AUCTeX with the following configuration.

(require 'tex)
(setq TeX-auto-save t)
(setq TeX-parse-self t)
(setq-default TeX-master "main")
(setq latex-run-command "pdflatex")

Trying to build my document with C-c C-a gives me the error

ERROR: Undefined control sequence.

--- TeX said ---
l.1 \documentclass{IEEEtran}

My main.tex file looks like this:

\documentclass{IEEEtran}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[ngerman]{babel}
\usepackage{caption}
\usepackage{graphicx}
\usepackage{import}
\usepackage{url}
\def\UrlBreaks{\do\/\do-}
\renewcommand\_{\textunderscore\allowbreak}

\begin{document}

\title{foo bar}
\author{foo}
\maketitle

\begin{abstract}
\end{abstract}

\begin{IEEEkeywords}
  Blockchain
\end{IEEEkeywords}


% Einleitung
\import{./}{intro.tex}


\nocite{*}
\bibliographystyle{unsrt}

\bibliography{references}



\end{document}

Using pdflatex on the terminal is just working fine.

Why does my emacs say different? I though internally is just a pdflatex call and... violá.