diff --git a/src/lisp/e_atan2.c b/src/lisp/e_atan2.c
index 7e177e8721092095207d6b2e743f9ee8fee898c7..a841ace2e37f68637f056543fa204f52b1955416 100644
--- a/src/lisp/e_atan2.c
+++ b/src/lisp/e_atan2.c
@@ -75,7 +75,7 @@ pi_lo   = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
 	if(((ix|((lx|-lx)>>31))>0x7ff00000)||
 	   ((iy|((ly|-ly)>>31))>0x7ff00000))	/* x or y is NaN */
 	   return x+y;
-	if((hx-0x3ff00000|lx)==0) return fdlibm_atan(y);   /* x=1.0 */
+	if(((hx-0x3ff00000)|lx)==0) return fdlibm_atan(y);   /* x=1.0 */
 	m = ((hy>>31)&1)|((hx>>30)&2);	/* 2*sign(x)+sign(y) */
 
     /* when y = 0 */