diff --git a/.travis.yml b/.travis.yml
index a6a29a396..5b06a779b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,7 +24,7 @@ before_install:
   - conda activate pypsa-eur
 
   # install open-source solver
-  - mamba install -c conda-forge glpk ipopt
+  - mamba install -c conda-forge glpk ipopt<3.13.3
 
   # list packages for easier debugging
   - conda list