diff --git a/CMake/BuildERFExe.cmake b/CMake/BuildERFExe.cmake
index e67a27fae..ff8610da5 100644
--- a/CMake/BuildERFExe.cmake
+++ b/CMake/BuildERFExe.cmake
@@ -27,7 +27,6 @@ function(build_erf_lib erf_lib_name)
 
   if(ERF_ENABLE_POISSON_SOLVE)
     target_sources(${erf_lib_name} PRIVATE
-                   ${SRC_DIR}/TimeIntegration/ERF_slow_rhs_inc.cpp
                    ${SRC_DIR}/Utils/ERF_PoissonSolve.cpp
                    ${SRC_DIR}/Utils/ERF_PoissonSolve_tb.cpp)
     target_compile_definitions(${erf_lib_name} PUBLIC ERF_USE_POISSON_SOLVE)