diff --git a/meson.build b/meson.build
index 64c3a5e9..af5befca 100644
--- a/meson.build
+++ b/meson.build
@@ -68,7 +68,6 @@ subdir('fuk95')
 subdir('channel')
 subdir('single_column')
 subdir('pkgs/')
-subdir('hamocc')
 
 # Handle options and add necessary flags and subfolders with source files
 
@@ -115,6 +114,7 @@ endif
 
 if get_option('ecosys')
   add_project_arguments('-DHAMOCC', language: 'fortran')
+  subdir('hamocc')
 endif
 
 if get_option('levitus2x')
diff --git a/trc/initrc.F b/trc/initrc.F
index eb1fc8ea..cf9d30a5 100644
--- a/trc/initrc.F
+++ b/trc/initrc.F
@@ -23,7 +23,9 @@ subroutine initrc
 c --- initialization of tracers
 c --- ------------------------------------------------------------------
 c
+#ifdef HAMOCC
       use mo_hamocc_init, only: hamocc_init
+#endif
 
       implicit none
 c
diff --git a/trc/restart_trcrd.F90 b/trc/restart_trcrd.F90
index 7811cc83..99b41f27 100644
--- a/trc/restart_trcrd.F90
+++ b/trc/restart_trcrd.F90
@@ -23,7 +23,10 @@ subroutine restart_trcrd(rstfnm_ocn)
 ! --- Read tracer state from restart files
 ! --- ------------------------------------------------------------------
 !
+#ifdef HAMOCC
   use mo_hamocc_init, only: hamocc_init
+#endif
+
   use mod_config, only: expcnf
   use mod_xc
 
diff --git a/trc/restart_trcwt.F90 b/trc/restart_trcwt.F90
index de73bb78..3e9e96ac 100644
--- a/trc/restart_trcwt.F90
+++ b/trc/restart_trcwt.F90
@@ -23,7 +23,9 @@ subroutine restart_trcwt(rstfnm_ocn)
 ! --- Write tracer state to restart files
 ! --- ------------------------------------------------------------------
 !
+#ifdef HAMOCC
   use mo_restart_hamoccwt, only : restart_hamoccwt
+#endif
   use mod_config, only: expcnf
   use mod_xc
 
diff --git a/trc/updtrc.F b/trc/updtrc.F
index 6c0df194..ec026935 100644
--- a/trc/updtrc.F
+++ b/trc/updtrc.F
@@ -23,7 +23,10 @@ subroutine updtrc(m,n,mm,nn,k1m,k1n)
 c --- update tracers due to non-passive processes
 c --- ------------------------------------------------------------------
 c
+#ifdef HAMOCC
       use mo_hamocc_step, only: hamocc_step
+#endif
+
       use mod_xc
 c
       implicit none