diff --git a/core/hw/pvr/Renderer_if.cpp b/core/hw/pvr/Renderer_if.cpp
index c9a4b2fe3..a15713528 100644
--- a/core/hw/pvr/Renderer_if.cpp
+++ b/core/hw/pvr/Renderer_if.cpp
@@ -581,9 +581,9 @@ void rend_vblank()
 
 void check_framebuffer_write()
 {
-	u32 fb_size = (FB_R_SIZE.fb_y_size + 1) * (FB_R_SIZE.fb_x_size + FB_R_SIZE.fb_modulus) / 4;
+	u32 fb_size = (FB_R_SIZE.fb_y_size + 1) * (FB_R_SIZE.fb_x_size + FB_R_SIZE.fb_modulus) * 4;
 	fb1_watch_addr_start = FB_R_SOF1 & VRAM_MASK;
-	fb1_watch_addr_end = fb1_watch_addr_start + fb_size - 1;
+	fb1_watch_addr_end = fb1_watch_addr_start + fb_size;
 	fb2_watch_addr_start = FB_R_SOF2 & VRAM_MASK;
-	fb2_watch_addr_end = fb2_watch_addr_start + fb_size - 1;
+	fb2_watch_addr_end = fb2_watch_addr_start + fb_size;
 }