diff --git a/apps/AmpGen.cpp b/apps/AmpGen.cpp
index 7c9aa11520..293d49a2b0 100644
--- a/apps/AmpGen.cpp
+++ b/apps/AmpGen.cpp
@@ -79,6 +79,7 @@ template <class T> void generateSource(T& pdf, const std::string& sourceFile, Mi
 
   double norm = 1; 
   if( normalise ){
+    INFO("Normalising PDF"); 
     TRandom3 rnd(seed);
     unsigned d_i = pdf.eventType().dim().first;
     Generator<PhaseSpace> phsp(pdf.eventType());
diff --git a/python/ampgen.py b/python/ampgen.py
index 214fb43ae7..1f69749adb 100644
--- a/python/ampgen.py
+++ b/python/ampgen.py
@@ -91,7 +91,7 @@ def make_ampgen_model( options_file, src = "" ) :
     if src == "" : src=mkstemp( suffix='.cpp')[1]
     lib=src.replace(".cpp",".so")
     if not os.path.isfile(lib) :
-        cmd = ["AmpGen", options_file, f"--Output {src}", "--Normalise=0", "--CompilerWrapper::Verbose=1"]
+        cmd = ["AmpGen", options_file, f"--Output {src}", "--Normalise=0", "--CompilerWrapper::Verbose=1", "--AutoCompile=0"]
         print( f"Running command {cmd}")
         subprocess.run(cmd, check=True, text=True)
     return AmpGenModel(os.path.abspath(lib))
diff --git a/src/CoherentSum.cpp b/src/CoherentSum.cpp
index 604a1a9237..a81703c3cb 100644
--- a/src/CoherentSum.cpp
+++ b/src/CoherentSum.cpp
@@ -9,6 +9,7 @@
 #include <numeric>
 #include <ratio>
 #include <thread>
+#include <csignal>
 
 #include "AmpGen/CompiledExpression.h"
 #include "AmpGen/ErrorPropagator.h"
@@ -45,6 +46,7 @@ CoherentSum::CoherentSum( const EventType& type, const MinuitParameterSet& mps,
   , m_prefix   (prefix)
       , m_mps(&mps) 
 {
+  bool autocompile = NamedParameter<bool>("AutoCompile", true); 
   auto rules = AmplitudeRules::create(mps);
   auto amplitudes      = rules->getMatchingRules( m_eventType, prefix);
   if( amplitudes.size() == 0 ){
@@ -56,19 +58,14 @@ CoherentSum::CoherentSum( const EventType& type, const MinuitParameterSet& mps,
   size_t      nThreads = NamedParameter<size_t>     ("nCores"    , std::thread::hardware_concurrency(), "Number of threads to use" );
   ThreadPool tp(nThreads);
   auto head_rules = rules->rulesForDecay(m_eventType.mother(), m_prefix);
-  /*
-  for( const auto& rule : head_rules )
-  {
-    auto indices = findIndices(m_matrixElements, rule.particle().decayDescriptor() );
-    INFO( rule.particle() << " [" << vectorToString(indices, " ") << "]" ); 
-  }
-  */
   for(size_t i = 0; i < m_matrixElements.size(); ++i){
-    tp.enqueue( [i, this, &mps, &amplitudes]() mutable {
+    auto task = [i, this, &mps, &amplitudes, autocompile]() mutable {
         this->m_matrixElements[i] = 
           MatrixElement(amplitudes[i].first, amplitudes[i].second, mps, this->m_eventType.getEventFormat(), this->m_dbThis);  
-        CompilerWrapper().compile( this->m_matrixElements[i], this->m_objCache); 
-    } ); 
+        if(autocompile) CompilerWrapper().compile( this->m_matrixElements[i], this->m_objCache); 
+    };
+    if( autocompile ) tp.enqueue( task ); 
+    else task(); 
   }
 }
 
@@ -77,10 +74,11 @@ void CoherentSum::prepare()
   transferParameters(); 
   ProfileClock clockEval; 
   for (auto& t : m_matrixElements ) {
-    if( not t.isReady() )
+    if( not t.isReady() ){
+      raise(SIGSEGV);
       FATAL( t.decayDescriptor() << " not ready, fix me"); 
+    }
     t.prepare();
-    
     if ( m_prepareCalls != 0 && !t.hasExternalsChanged() ) continue;
     if ( m_events != nullptr ) m_cache.update(t);
     m_integrator.updateCache(t);