diff --git a/ppu.cpp b/ppu.cpp
index 36e38f4c..e760c86f 100644
--- a/ppu.cpp
+++ b/ppu.cpp
@@ -1752,6 +1752,8 @@ void S9xSetCPU (uint8 Byte, uint16 Address)
 					}
 					else
 						CPU.FastROMSpeed = SLOW_ONE_CYCLE;
+					// we might currently be in FastROMSpeed region, S9xSetPCBase will update CPU.MemSpeed
+					S9xSetPCBase(Registers.PBPC);
 				}
 
 				break;