diff --git a/lib/init-7.scm b/lib/init-7.scm
index 64e21dc6..83ed8d6f 100644
--- a/lib/init-7.scm
+++ b/lib/init-7.scm
@@ -1175,7 +1175,7 @@
         (if (and (inf? x) (inf? y))
             (* (if (< y 0) -1 1) (if (= x -inf.0) 3 1) 0.7853981633974483)
             (if (negative? x)
-                (if (negative? y)
+                (if (or (negative? y) (eqv? y -0.0))
                     (- (atan1 (/ y x)) 3.141592653589793)
                     (- 3.141592653589793 (atan1 (/ y (- x)))))
                 (if (and (zero? x) (zero? y))