diff --git a/src/game_switches.cpp b/src/game_switches.cpp
index a68bb29918..ecb2b52779 100644
--- a/src/game_switches.cpp
+++ b/src/game_switches.cpp
@@ -21,6 +21,8 @@
 #include "output.h"
 #include "reader_util.h"
 
+constexpr int kMaxWarnings = 10;
+
 Game_Switches_Class::Game_Switches_Class() {}
 
 static std::vector<bool>& switches() {
@@ -28,6 +30,10 @@ static std::vector<bool>& switches() {
 }
 
 bool Game_Switches_Class::Get(int switch_id) const {
+	if ((switch_id <= 0 || switch_id > Data::switches.size()) && _warnings < kMaxWarnings) {
+		Output::Debug("Invalid read sw[%d]!", switch_id);
+		++_warnings;
+	}
 	auto& sv = switches();
 	if (switch_id <= 0 || switch_id > sv.size()) {
 		return false;
@@ -36,6 +42,10 @@ bool Game_Switches_Class::Get(int switch_id) const {
 }
 
 void Game_Switches_Class::Set(int switch_id, bool value) {
+	if ((switch_id <= 0 || switch_id > Data::switches.size()) && _warnings < kMaxWarnings) {
+		Output::Debug("Invalid write sw[%d] = %d!", switch_id, value);
+		++_warnings;
+	}
 	auto& sv = switches();
 	if (switch_id <= 0) {
 		return;
@@ -71,4 +81,5 @@ int Game_Switches_Class::GetSize() const {
 
 void Game_Switches_Class::Reset() {
 	switches().clear();
+	_warnings = 0;
 }
diff --git a/src/game_switches.h b/src/game_switches.h
index 327a532884..32cbc6d659 100644
--- a/src/game_switches.h
+++ b/src/game_switches.h
@@ -44,7 +44,7 @@ class Game_Switches_Class {
 	void Reset();
 
 private:
-	std::vector<bool> dummy;
+	mutable int _warnings = 0;
 };
 
 
diff --git a/src/game_variables.cpp b/src/game_variables.cpp
index b87f51b6a0..10bf648f35 100644
--- a/src/game_variables.cpp
+++ b/src/game_variables.cpp
@@ -22,6 +22,8 @@
 #include "player.h"
 #include "reader_util.h"
 
+constexpr int kMaxWarnings = 10;
+
 Game_Variables_Class::Game_Variables_Class() {}
 
 static std::vector<int32_t>& variables() {
@@ -29,6 +31,10 @@ static std::vector<int32_t>& variables() {
 }
 
 int Game_Variables_Class::Get(int variable_id) const {
+	if ((variable_id <= 0 || variable_id > Data::variables.size()) && _warnings < kMaxWarnings) {
+		Output::Debug("Invalid read var[%d]!", variable_id);
+		++_warnings;
+	}
 	auto& vv = variables();
 	if (variable_id <= 0 || variable_id > vv.size()) {
 		return 0;
@@ -37,6 +43,10 @@ int Game_Variables_Class::Get(int variable_id) const {
 }
 
 void Game_Variables_Class::Set(int variable_id, int value) {
+	if ((variable_id <= 0 || variable_id > Data::variables.size()) && _warnings < kMaxWarnings) {
+		Output::Debug("Invalid write var[%d] = %d!", variable_id, value);
+		++_warnings;
+	}
 	auto& vv = variables();
 	if (variable_id <= 0) {
 		return;
@@ -70,4 +80,5 @@ int Game_Variables_Class::GetSize() const {
 
 void Game_Variables_Class::Reset() {
 	variables().clear();
+	_warnings = 0;
 }
diff --git a/src/game_variables.h b/src/game_variables.h
index 85526ea880..296644089f 100644
--- a/src/game_variables.h
+++ b/src/game_variables.h
@@ -40,6 +40,8 @@ class Game_Variables_Class {
 	int GetSize() const;
 
 	void Reset();
+private:
+	mutable int _warnings = 0;
 };
 
 // Global variable