diff --git a/src/ObjLoading/Game/IW4/Menu/MenuConverterIW4.cpp b/src/ObjLoading/Game/IW4/Menu/MenuConverterIW4.cpp
index 6aa08ac6..a2cae9a8 100644
--- a/src/ObjLoading/Game/IW4/Menu/MenuConverterIW4.cpp
+++ b/src/ObjLoading/Game/IW4/Menu/MenuConverterIW4.cpp
@@ -12,6 +12,7 @@
 #include "Parsing/Simple/Expression/SimpleExpressionConditionalOperator.h"
 #include "Parsing/Simple/Expression/SimpleExpressionUnaryOperation.h"
 #include "Utils/ClassUtils.h"
+#include "Utils/StringUtils.h"
 
 #include <cassert>
 #include <cstring>
@@ -204,12 +205,15 @@ namespace IW4
                                                       const CommonMenuDef* menu,
                                                       const CommonItemDef* item) const
         {
-            Statement_s* functionStatement = m_conversion_zone_state->FindFunction(functionCall->m_function_name);
+            std::string lowerCaseFunctionName(functionCall->m_function_name);
+            utils::MakeStringLowerCase(lowerCaseFunctionName);
+
+            Statement_s* functionStatement = m_conversion_zone_state->FindFunction(lowerCaseFunctionName);
 
             if (functionStatement == nullptr)
             {
                 // Function was not converted yet: Convert it now
-                const auto foundCommonFunction = m_parsing_zone_state->m_functions_by_name.find(functionCall->m_function_name);
+                const auto foundCommonFunction = m_parsing_zone_state->m_functions_by_name.find(lowerCaseFunctionName);
 
                 if (foundCommonFunction == m_parsing_zone_state->m_functions_by_name.end())
                     throw MenuConversionException("Failed to find definition for custom function \"" + functionCall->m_function_name + "\"", menu, item);
diff --git a/src/ObjLoading/Game/IW5/Menu/MenuConverterIW5.cpp b/src/ObjLoading/Game/IW5/Menu/MenuConverterIW5.cpp
index 2da2a9da..321146fc 100644
--- a/src/ObjLoading/Game/IW5/Menu/MenuConverterIW5.cpp
+++ b/src/ObjLoading/Game/IW5/Menu/MenuConverterIW5.cpp
@@ -12,6 +12,7 @@
 #include "Parsing/Simple/Expression/SimpleExpressionConditionalOperator.h"
 #include "Parsing/Simple/Expression/SimpleExpressionUnaryOperation.h"
 #include "Utils/ClassUtils.h"
+#include "Utils/StringUtils.h"
 
 #include <cassert>
 #include <cstring>
@@ -204,18 +205,21 @@ namespace IW5
                                                       const CommonMenuDef* menu,
                                                       const CommonItemDef* item) const
         {
-            Statement_s* functionStatement = m_conversion_zone_state->FindFunction(functionCall->m_function_name);
+            std::string lowerCaseFunctionName(functionCall->m_function_name);
+            utils::MakeStringLowerCase(lowerCaseFunctionName);
+
+            Statement_s* functionStatement = m_conversion_zone_state->FindFunction(lowerCaseFunctionName);
 
             if (functionStatement == nullptr)
             {
                 // Function was not converted yet: Convert it now
-                const auto foundCommonFunction = m_parsing_zone_state->m_functions_by_name.find(functionCall->m_function_name);
+                const auto foundCommonFunction = m_parsing_zone_state->m_functions_by_name.find(lowerCaseFunctionName);
 
                 if (foundCommonFunction == m_parsing_zone_state->m_functions_by_name.end())
                     throw MenuConversionException("Failed to find definition for custom function \"" + functionCall->m_function_name + "\"", menu, item);
 
                 functionStatement = ConvertExpression(foundCommonFunction->second->m_value.get(), menu, item);
-                functionStatement = m_conversion_zone_state->AddFunction(foundCommonFunction->second->m_name, functionStatement);
+                functionStatement = m_conversion_zone_state->AddFunction(lowerCaseFunctionName, functionStatement);
             }
 
             expressionEntry functionEntry{};
diff --git a/src/ObjLoading/Parsing/Menu/MenuAssetZoneState.cpp b/src/ObjLoading/Parsing/Menu/MenuAssetZoneState.cpp
index 0b3a8eb9..cf9c5191 100644
--- a/src/ObjLoading/Parsing/Menu/MenuAssetZoneState.cpp
+++ b/src/ObjLoading/Parsing/Menu/MenuAssetZoneState.cpp
@@ -1,10 +1,15 @@
 #include "MenuAssetZoneState.h"
 
+#include "Utils/StringUtils.h"
+
 using namespace menu;
 
 void MenuAssetZoneState::AddFunction(std::unique_ptr<CommonFunctionDef> function)
 {
-    m_functions_by_name.emplace(std::make_pair(function->m_name, function.get()));
+    std::string lowerCaseFunctionName(function->m_name);
+    utils::MakeStringLowerCase(lowerCaseFunctionName);
+
+    m_functions_by_name.emplace(std::make_pair(lowerCaseFunctionName, function.get()));
     m_functions.emplace_back(std::move(function));
 }
 
diff --git a/src/ObjLoading/Parsing/Menu/MenuFileParserState.cpp b/src/ObjLoading/Parsing/Menu/MenuFileParserState.cpp
index 64fe0ffa..9cb3af8a 100644
--- a/src/ObjLoading/Parsing/Menu/MenuFileParserState.cpp
+++ b/src/ObjLoading/Parsing/Menu/MenuFileParserState.cpp
@@ -1,5 +1,7 @@
 #include "MenuFileParserState.h"
 
+#include "Utils/StringUtils.h"
+
 using namespace menu;
 
 MenuFileParserState::EventHandlerConditionState::EventHandlerConditionState(CommonEventHandlerCondition* condition)
@@ -32,7 +34,9 @@ MenuFileParserState::MenuFileParserState(const FeatureLevel featureLevel, const
 {
     for (const auto& function : zoneState->m_functions)
     {
-        m_functions_by_name.emplace(std::make_pair(function->m_name, function.get()));
+        std::string lowerCaseName(function->m_name);
+        utils::MakeStringLowerCase(lowerCaseName);
+        m_functions_by_name.emplace(std::make_pair(lowerCaseName, function.get()));
     }
 
     for (const auto& menu : zoneState->m_menus)