diff --git a/src/script_opt/ScriptOpt.cc b/src/script_opt/ScriptOpt.cc
index fcc2f32fe3..18a5b9d33a 100644
--- a/src/script_opt/ScriptOpt.cc
+++ b/src/script_opt/ScriptOpt.cc
@@ -370,6 +370,8 @@ static void use_CPP()
 	if ( ! CPP_init_hook )
 		reporter->FatalError("no C++ functions available to use");
 
+	int num_used = 0;
+
 	for ( auto& f : funcs )
 		{
 		auto hash = f.Profile()->HashVal();
@@ -377,6 +379,8 @@ static void use_CPP()
 
 		if ( s != compiled_scripts.end() )
 			{
+			++num_used;
+
 			auto b = s->second.body;
 			b->SetHash(hash);
 
@@ -407,6 +411,9 @@ static void use_CPP()
 			}
 		}
 
+	if ( num_used == 0 )
+		reporter->FatalError("no C++ functions found to use");
+
 	// Now that we've loaded all of the compiled scripts
 	// relevant for the AST, activate standalone ones.
 	for ( auto cb : standalone_activations )