diff --git a/CMakeLists.txt b/CMakeLists.txt
index abb900592a..208da7b41c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -108,8 +108,8 @@ if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU)
   endif()
 
   # GCC compiler options
-  list(APPEND f90flags -cpp -std=f2008 -fbacktrace)
-  list(APPEND cflags -cpp -std=c99)
+  list(APPEND f90flags -cpp -std=f2008 -fbacktrace -O2)
+  list(APPEND cflags -cpp -std=c99 -O2)
   if(debug)
     list(APPEND f90flags -g -Wall -pedantic -fbounds-check
       -ffpe-trap=invalid,overflow,underflow)
@@ -122,6 +122,8 @@ if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU)
     list(APPEND ldflags -pg)
   endif()
   if(optimize)
+    list(REMOVE_ITEM f90flags -O2)
+    list(REMOVE_ITEM cflags -O2)
     list(APPEND f90flags -O3)
     list(APPEND cflags -O3)
   endif()
@@ -190,6 +192,7 @@ elseif(CMAKE_Fortran_COMPILER_ID STREQUAL XL)
     list(APPEND ldflags -p)
   endif()
   if(optimize)
+    list(REMOVE_ITEM f90flags -O2)
     list(APPEND f90flags -O3)
   endif()
   if(openmp)