snakemake conda env cannot be created from environment.yml

Creating the environment with

conda create -n rnaseq_pipeline -c bioconda -c conda-forge snakemake=5.10.0

works fine, whereas

conda env create -f environment.yml

with

name: rnaseq_pipeline
channels:
  - bioconda
  - conda-forge
dependencies:
  - snakemake=5.10.0

just never finishes solving the environment. The same environment file with 'mongoengine' instead of 'snakemake' works fine.

conda version: 4.8.2