diff --git a/src/gl_draw.c b/src/gl_draw.c
index e9cc352..2277f13 100644
--- a/src/gl_draw.c
+++ b/src/gl_draw.c
@@ -817,7 +817,8 @@ void keyboard(unsigned char key, int x, int y)
 		glutPostRedisplay();
 		break;
 	case 'K':
-		ball_speed -= 0.2f;
+		if (ball_speed - 0.2f > 0)
+			ball_speed -= 0.2f;
 		glutPostRedisplay();
 		break;
 	case 'f':