diff --git a/src/main.c b/src/main.c
index 78f4414fe..f16ba1c9d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2417,7 +2417,7 @@ int main(int argc, char *argv[])
 						{
 							for (j=-bsy; j<=bsy; j++)
 								for (i=-bsx; i<=bsx; i++)
-									if ((CURRENT_BRUSH==CIRCLE_BRUSH && (pow(i,2))/(pow(bsx,2))+(pow(j,2))/(pow(bsy,2))<=1)||(CURRENT_BRUSH==SQUARE_BRUSH&&i*j<=bsy*bsx))
+									if (x+i>0 && y+j>0 && x+i<XRES && y+j<YRES && ((CURRENT_BRUSH==CIRCLE_BRUSH && (pow(i,2))/(pow(bsx,2))+(pow(j,2))/(pow(bsy,2))<=1)||(CURRENT_BRUSH==SQUARE_BRUSH&&i*j<=bsy*bsx)))
 									{
 										vx[(y+j)/CELL][(x+i)/CELL] += (x-lx)*0.01f;
 										vy[(y+j)/CELL][(x+i)/CELL] += (y-ly)*0.01f;