diff --git a/src/classes/CMakeLists.txt b/src/classes/CMakeLists.txt
index adbe2175..0038b08f 100644
--- a/src/classes/CMakeLists.txt
+++ b/src/classes/CMakeLists.txt
@@ -110,6 +110,10 @@ target_include_directories(
   PUserFcnBase BEFORE PRIVATE $<BUILD_INTERFACE:${MUSRFIT_INC}>
 )
 
+#--- add compile options for optimization -------------------------------------
+target_compile_options(PMusr PUBLIC -O2)
+target_compile_options(PUserFcnBase PUBLIC -O2)
+
 #--- add OpenMP compile options if needed -------------------------------------
 if (OpenMP_FOUND)
   target_compile_options(PMusr PUBLIC ${OpenMP_CXX_FLAGS})