diff --git a/schedulers/tetrisched/CMakeLists.txt b/schedulers/tetrisched/CMakeLists.txt
index 8d2699bb..b9eee3e9 100644
--- a/schedulers/tetrisched/CMakeLists.txt
+++ b/schedulers/tetrisched/CMakeLists.txt
@@ -23,7 +23,7 @@ FetchContent_MakeAvailable(googletest)
 
 # Set the directories where the solver backends are installed.
 if (DEFINED ENV{CPLEX_DIR})
-    set(CPLEX_DIR ENV{CPLEX_DIR})
+    set(CPLEX_DIR $ENV{CPLEX_DIR})
     message("-- Using CPLEX installation at: ${CPLEX_DIR}")
 else()
     set(CPLEX_DIR "/opt/ibm/ILOG/CPLEX_Studio2211")
@@ -31,7 +31,7 @@ else()
 endif()
 
 if (DEFINED ENV{GUROBI_DIR})
-   set(GUROBI_DIR ENV{GUROBI_DIR})
+   set(GUROBI_DIR $ENV{GUROBI_DIR})
    message("-- Using Gurobi installation at: ${GUROBI_DIR}")
 else()
    set(GUROBI_DIR "/opt/gurobi1001/linux64")
@@ -39,7 +39,7 @@ else()
 endif()
 
 if (DEFINED ENV{ORTOOLS_DIR})
-   set(ORTOOLS_DIR ENV{ORTOOLS_DIR})
+   set(ORTOOLS_DIR $ENV{ORTOOLS_DIR})
    message("-- Using Google OR-Tools installation at: ${ORTOOLS_DIR}")
 else()
    set(ORTOOLS_DIR "/usr/local/include/ortools")