diff --git a/.travis.yml b/.travis.yml
index f08cd97e..17bdb73a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,8 +20,7 @@ before_install:
   - conda activate pypsa-eur
 
   # install open-source solver
-  - mamba install -c conda-forge glpk
-  - conda install -c conda-forge ipopt
+  - mamba install -c conda-forge glpk ipopt
 
   # list packages for easier debugging
   - conda list