diff --git a/rpcs3/Emu/Cell/Modules/cellRtc.cpp b/rpcs3/Emu/Cell/Modules/cellRtc.cpp
index 1186abd656..d4b4db4bb9 100644
--- a/rpcs3/Emu/Cell/Modules/cellRtc.cpp
+++ b/rpcs3/Emu/Cell/Modules/cellRtc.cpp
@@ -1020,7 +1020,8 @@ error_code cellRtcTickAddMonths(vm::ptr<CellRtcTick> pTick0, vm::cptr<CellRtcTic
 		return CELL_RTC_ERROR_INVALID_ARG;
 	}
 
-	u32 uVar1 = ((unk_1 * 0x51eb851f) >> 0x20);
+	u32 uVar1 = ((s64{unk_1} * 0x51eb851f) >> 0x20);
+
 	// Leap year check
 	u32 month_idx;
 	if ((unk_1 == (uVar1 >> 7) * 400) || ((unk_1 != (uVar1 >> 5) * 100 && ((unk_2 & 3) == 0))))
@@ -1069,7 +1070,8 @@ error_code cellRtcTickAddYears(vm::ptr<CellRtcTick> pTick0, vm::cptr<CellRtcTick
 		return CELL_RTC_ERROR_INVALID_ARG;
 	}
 
-	u32 uVar1 = ((unk_1 * 0x51eb851f) >> 0x20);
+	u32 uVar1 = ((s64{unk_1} * 0x51eb851f) >> 0x20);
+
 	// Leap year check
 	u32 month_idx;
 	if ((unk_1 == (uVar1 >> 7) * 400) || ((unk_1 != (uVar1 >> 5) * 100 && ((total_years & 3) == 0))))