diff --git a/src/currency.cpp b/src/currency.cpp
index f7dfabb370..6d2f2e3be4 100644
--- a/src/currency.cpp
+++ b/src/currency.cpp
@@ -85,8 +85,7 @@ std::array<CurrencySpec, CURRENCY_END> _currency_specs;
  * When a grf sends currencies, they are based on the order defined by TTDPatch.
  * So, we must reindex them to our own order.
  */
-const uint8_t TTDPatch_To_OTTDIndex[] =
-{
+const Currency _ttdpatch_to_ottd_currency[] = {
 	CURRENCY_GBP,
 	CURRENCY_USD,
 	CURRENCY_FRF,
@@ -114,11 +113,12 @@ const uint8_t TTDPatch_To_OTTDIndex[] =
  * it is a grf written for ottd, thus returning the same id.
  * Only called from newgrf.cpp
  * @param grfcurr_id currency id coming from newgrf
- * @return the corrected index
+ * @return The corrected index, or \c CURRENCY_END when invalid.
  */
-uint8_t GetNewgrfCurrencyIdConverted(uint8_t grfcurr_id)
+Currency GetNewgrfCurrencyIdConverted(uint8_t grfcurr_id)
 {
-	return (grfcurr_id >= lengthof(TTDPatch_To_OTTDIndex)) ? grfcurr_id : TTDPatch_To_OTTDIndex[grfcurr_id];
+	if (grfcurr_id >= std::size(_ttdpatch_to_ottd_currency)) return CURRENCY_END;
+	return _ttdpatch_to_ottd_currency[grfcurr_id];
 }
 
 /**
diff --git a/src/currency_func.h b/src/currency_func.h
index 9b73902ab2..0713cd5931 100644
--- a/src/currency_func.h
+++ b/src/currency_func.h
@@ -35,6 +35,6 @@ inline const CurrencySpec &GetCurrency()
 
 Currencies GetMaskOfAllowedCurrencies();
 void ResetCurrencies(bool preserve_custom = true);
-uint8_t GetNewgrfCurrencyIdConverted(uint8_t grfcurr_id);
+Currency GetNewgrfCurrencyIdConverted(uint8_t grfcurr_id);
 
 #endif /* CURRENCY_FUNC_H */
diff --git a/src/newgrf/newgrf_act0_globalvar.cpp b/src/newgrf/newgrf_act0_globalvar.cpp
index 3fd244748c..6f78be220a 100644
--- a/src/newgrf/newgrf_act0_globalvar.cpp
+++ b/src/newgrf/newgrf_act0_globalvar.cpp
@@ -146,7 +146,7 @@ static ChangeInfoResult GlobalVarChangeInfo(uint first, uint last, int prop, Byt
 			}
 
 			case 0x0A: { // Currency display names
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				if (curidx < CURRENCY_END) {
 					AddStringForMapping(GRFStringID{buf.ReadWord()}, [curidx](StringID str) {
 						_currency_specs[curidx].name = str;
@@ -159,7 +159,7 @@ static ChangeInfoResult GlobalVarChangeInfo(uint first, uint last, int prop, Byt
 			}
 
 			case 0x0B: { // Currency multipliers
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				uint32_t rate = buf.ReadDWord();
 
 				if (curidx < CURRENCY_END) {
@@ -168,13 +168,13 @@ static ChangeInfoResult GlobalVarChangeInfo(uint first, uint last, int prop, Byt
 					 * to be compatible */
 					_currency_specs[curidx].rate = rate / 1000;
 				} else {
-					GrfMsg(1, "GlobalVarChangeInfo: Currency multipliers {} out of range, ignoring", curidx);
+					GrfMsg(1, "GlobalVarChangeInfo: Currency multipliers {} out of range, ignoring", id);
 				}
 				break;
 			}
 
 			case 0x0C: { // Currency options
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				uint16_t options = buf.ReadWord();
 
 				if (curidx < CURRENCY_END) {
@@ -185,43 +185,43 @@ static ChangeInfoResult GlobalVarChangeInfo(uint first, uint last, int prop, Byt
 					 * since newgrf specs said that only 0 and 1 can be set for symbol_pos */
 					_currency_specs[curidx].symbol_pos = HasBit(options, 8) ? CurrencySymbolPosition::Suffix : CurrencySymbolPosition::Prefix;
 				} else {
-					GrfMsg(1, "GlobalVarChangeInfo: Currency option {} out of range, ignoring", curidx);
+					GrfMsg(1, "GlobalVarChangeInfo: Currency option {} out of range, ignoring", id);
 				}
 				break;
 			}
 
 			case 0x0D: { // Currency prefix symbol
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				std::string prefix = ReadDWordAsString(buf);
 
 				if (curidx < CURRENCY_END) {
 					_currency_specs[curidx].prefix = std::move(prefix);
 				} else {
-					GrfMsg(1, "GlobalVarChangeInfo: Currency symbol {} out of range, ignoring", curidx);
+					GrfMsg(1, "GlobalVarChangeInfo: Currency symbol {} out of range, ignoring", id);
 				}
 				break;
 			}
 
 			case 0x0E: { // Currency suffix symbol
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				std::string suffix = ReadDWordAsString(buf);
 
 				if (curidx < CURRENCY_END) {
 					_currency_specs[curidx].suffix = std::move(suffix);
 				} else {
-					GrfMsg(1, "GlobalVarChangeInfo: Currency symbol {} out of range, ignoring", curidx);
+					GrfMsg(1, "GlobalVarChangeInfo: Currency symbol {} out of range, ignoring", id);
 				}
 				break;
 			}
 
 			case 0x0F: { //  Euro introduction dates
-				uint curidx = GetNewgrfCurrencyIdConverted(id);
+				Currency curidx = GetNewgrfCurrencyIdConverted(id);
 				TimerGameCalendar::Year year_euro{buf.ReadWord()};
 
 				if (curidx < CURRENCY_END) {
 					_currency_specs[curidx].to_euro = year_euro;
 				} else {
-					GrfMsg(1, "GlobalVarChangeInfo: Euro intro date {} out of range, ignoring", curidx);
+					GrfMsg(1, "GlobalVarChangeInfo: Euro intro date {} out of range, ignoring", id);
 				}
 				break;
 			}