diff --git a/inst/cta/src/GCTAOnOffObservation.cpp b/inst/cta/src/GCTAOnOffObservation.cpp
index 32a3c12..af2f166 100644
--- a/inst/cta/src/GCTAOnOffObservation.cpp
+++ b/inst/cta/src/GCTAOnOffObservation.cpp
@@ -46,6 +46,11 @@
 #include "GCTAModelIrfBackground.hpp"
 #include "GCTAOnOffObservation.hpp"
 
+/* __ OpenMP section _____________________________________________________ */
+#ifdef _OPENMP
+#include <omp.h>
+#endif
+
 /* __ Globals ____________________________________________________________ */
 const GCTAOnOffObservation g_onoff_obs_cta_seed;
 const GObservationRegistry g_onoff_obs_cta_registry(&g_onoff_obs_cta_seed);
@@ -529,8 +534,12 @@ double GCTAOnOffObservation::likelihood(const GModels& models,
 {
     // Timing measurement
     #if defined(G_LIKELIHOOD_DEBUG)
+    #ifdef _OPENMP
+    double t_start = omp_get_wtime();
+    #else
     clock_t t_start = clock();
     #endif
+    #endif
 	
     // Initialise statistics
     #if defined(G_LIKELIHOOD_DEBUG)