diff --git a/src/economy.cpp b/src/economy.cpp
index 57d052beaf..1d934bd7c5 100644
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -109,7 +109,7 @@ int _score_part[MAX_COMPANIES][SCORE_END];
 Economy _economy;
 Prices _price;
 Money _additional_cash_required;
-static byte _price_base_multiplier[PR_END];
+static int8 _price_base_multiplier[PR_END];
 
 Money CalculateCompanyValue(const Company *c)
 {
@@ -652,7 +652,7 @@ void RecomputePrices()
 		price = (int64)price * _economy.inflation_prices;
 
 		/* Apply newgrf modifiers, and remove fractional part of inflation */
-		int shift = _price_base_multiplier[i] - 8 - 16;
+		int shift = _price_base_multiplier[i] - 16;
 		if (shift >= 0) {
 			price <<= shift;
 		} else {
@@ -728,22 +728,20 @@ static void HandleEconomyFluctuations()
  */
 void ResetPriceBaseMultipliers()
 {
-	/* 8 means no multiplier. */
-	for (Price i = PR_BEGIN; i < PR_END; i++)
-		_price_base_multiplier[i] = 8;
+	memset(_price_base_multiplier, 0, sizeof(_price_base_multiplier));
 }
 
 /**
  * Change a price base by the given factor.
- * The price base is altered by factors of two, with an offset of 8.
- * NewBaseCost = OldBaseCost * 2^(n-8)
+ * The price base is altered by factors of two.
+ * NewBaseCost = OldBaseCost * 2^n
  * @param price Index of price base to change.
  * @param factor Amount to change by.
  */
-void SetPriceBaseMultiplier(Price price, byte factor)
+void SetPriceBaseMultiplier(Price price, int factor)
 {
 	assert(price < PR_END);
-	_price_base_multiplier[price] = min(factor, MAX_PRICE_MODIFIER);
+	_price_base_multiplier[price] = Clamp(factor, MIN_PRICE_MODIFIER, MAX_PRICE_MODIFIER);
 }
 
 /**
diff --git a/src/economy_func.h b/src/economy_func.h
index 9a84635c0c..38505d4504 100644
--- a/src/economy_func.h
+++ b/src/economy_func.h
@@ -23,7 +23,7 @@
 #include "station_type.h"
 
 void ResetPriceBaseMultipliers();
-void SetPriceBaseMultiplier(Price price, byte factor);
+void SetPriceBaseMultiplier(Price price, int factor);
 
 extern const ScoreInfo _score_info[];
 extern int _score_part[MAX_COMPANIES][SCORE_END];
diff --git a/src/economy_type.h b/src/economy_type.h
index 4d726ed5d3..ccaf9de4ad 100644
--- a/src/economy_type.h
+++ b/src/economy_type.h
@@ -171,11 +171,14 @@ static const int LOAN_INTERVAL = 10000;
 static const uint64 MAX_INFLATION = (1ull << (63 - 32)) - 1;
 
 /**
- * Maximum NewGRF price modifier including the shift offset of 8 bits.
+ * Maximum NewGRF price modifiers.
  * Increasing base prices by factor 65536 should be enough.
  * @see MAX_INFLATION
  */
-static const int MAX_PRICE_MODIFIER = 16 + 8;
+enum {
+	MIN_PRICE_MODIFIER = -8,
+	MAX_PRICE_MODIFIER = 16,
+};
 
 struct CargoPayment;
 typedef uint32 CargoPaymentID;
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 69a187fd6e..caa30ebb4b 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -1665,11 +1665,11 @@ static ChangeInfoResult GlobalVarChangeInfo(uint gvid, int numinfo, int prop, by
 	for (int i = 0; i < numinfo; i++) {
 		switch (prop) {
 			case 0x08: { // Cost base factor
-				byte factor = grf_load_byte(&buf);
+				int factor = grf_load_byte(&buf);
 				uint price = gvid + i;
 
 				if (price < PR_END) {
-					SetPriceBaseMultiplier((Price)price, factor);
+					SetPriceBaseMultiplier((Price)price, factor - 8);
 				} else {
 					grfmsg(1, "GlobalVarChangeInfo: Price %d out of range, ignoring", price);
 				}