diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 666b77ae3d..48557a43f3 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -76,7 +76,7 @@ add_definitions(-DLAMMPS_MEMALIGN=${LAMMPS_MEMALIGN})
 option(LAMMPS_EXCEPTIONS "enable the use of C++ exceptions for error messages (useful for library interface)" OFF)
 if(LAMMPS_EXCEPTIONS)
   add_definitions(-DLAMMPS_EXCEPTIONS)
-  set(LAMMPS_API_DEFINES "${LAMMPS_API_DEFINES -DLAMMPS_EXCEPTIONS")
+  set(LAMMPS_API_DEFINES "${LAMMPS_API_DEFINES} -DLAMMPS_EXCEPTIONS")
 endif()
 
 set(LAMMPS_MACHINE "" CACHE STRING "Suffix to append to lmp binary and liblammps (WON'T enable any features automatically")