diff --git a/src/lib/ecs/system/ShipSystem.cpp b/src/lib/ecs/system/ShipSystem.cpp
index d3762f7..c2688e4 100644
--- a/src/lib/ecs/system/ShipSystem.cpp
+++ b/src/lib/ecs/system/ShipSystem.cpp
@@ -2,6 +2,7 @@
 
 #include <cassert>
 #include <map>
+#include <stdexcept>
 #include <utility>
 #include <vector>
 
@@ -102,7 +103,7 @@ entt::entity ShipSystem::spawn(const std::string& schematicId, int level,
     for (const PlacedModule& pm : modules)
     {
         const ModuleDef* modDef = findModuleDef(pm.moduleId);
-        if (!modDef) { continue; }
+        if (!modDef) { throw std::runtime_error("unknown module id '" + pm.moduleId + "'"); }
 
         const double mx = static_cast<double>(modDef->playerProductionLevel);
 
@@ -173,7 +174,7 @@ entt::entity ShipSystem::spawn(const std::string& schematicId, int level,
     for (const PlacedModule& pm : modules)
     {
         const ModuleDef* modDef = findModuleDef(pm.moduleId);
-        if (!modDef) { continue; }
+        if (!modDef) { throw std::runtime_error("unknown module id '" + pm.moduleId + "'"); }
 
         const double mx = static_cast<double>(modDef->playerProductionLevel);
 
diff --git a/src/lib/sim/ShipStatsCalculator.cpp b/src/lib/sim/ShipStatsCalculator.cpp
index d9cb2b1..1716400 100644
--- a/src/lib/sim/ShipStatsCalculator.cpp
+++ b/src/lib/sim/ShipStatsCalculator.cpp
@@ -1,6 +1,7 @@
 #include "ShipStatsCalculator.h"
 
 #include <map>
+#include <stdexcept>
 #include <utility>
 
 #include "DynamicBodyComponent.h"
@@ -67,7 +68,7 @@ ShipStats calculateShipStats(const GameConfig& config,
     for (const PlacedModule& pm : modules)
     {
         const ModuleDef* def = findModuleDef(pm.moduleId);
-        if (!def) { continue; }
+        if (!def) { throw std::runtime_error("unknown module id '" + pm.moduleId + "'"); }
 
         const double mx = static_cast<double>(def->playerProductionLevel);
 
@@ -105,7 +106,7 @@ ShipStats calculateShipStats(const GameConfig& config,
     for (const PlacedModule& pm : modules)
     {
         const ModuleDef* def = findModuleDef(pm.moduleId);
-        if (!def) { continue; }
+        if (!def) { throw std::runtime_error("unknown module id '" + pm.moduleId + "'"); }
 
         const double mx = static_cast<double>(def->playerProductionLevel);