diff --git a/MIP/package.yaml b/MIP/package.yaml
index 09f2bec..dcd39b1 100644
--- a/MIP/package.yaml
+++ b/MIP/package.yaml
@@ -77,7 +77,7 @@ library:
   - filepath
   - intern >=0.9.1.2 && <1.0.0.0
   - megaparsec >=5 && <10
-  - mtl >=2.1.2
+  - mtl >=2.1.2 && <2.4
   - OptDir
   - process >=1.1.0.2
   - scientific
diff --git a/MIP/src/Numeric/Optimization/MIP/Solution/CBC.hs b/MIP/src/Numeric/Optimization/MIP/Solution/CBC.hs
index 86f7aa6..08ad7e4 100644
--- a/MIP/src/Numeric/Optimization/MIP/Solution/CBC.hs
+++ b/MIP/src/Numeric/Optimization/MIP/Solution/CBC.hs
@@ -24,6 +24,7 @@ import Prelude hiding (readFile, writeFile)
 import Control.Applicative
 #endif
 
+import Control.Monad (foldM)
 import Control.Monad.Except
 import Data.Interned (intern)
 import Data.Map (Map)
diff --git a/MIP/src/Numeric/Optimization/MIP/Solution/SCIP.hs b/MIP/src/Numeric/Optimization/MIP/Solution/SCIP.hs
index b1aa34b..ed41d12 100644
--- a/MIP/src/Numeric/Optimization/MIP/Solution/SCIP.hs
+++ b/MIP/src/Numeric/Optimization/MIP/Solution/SCIP.hs
@@ -23,6 +23,7 @@ import Prelude hiding (readFile, writeFile)
 #if !MIN_VERSION_base(4,8,0)
 import Control.Applicative
 #endif
+import Control.Monad (foldM)
 import Control.Monad.Except
 import Data.Interned (intern)
 import Data.Map (Map)