diff --git a/ice-9/format.scm b/ice-9/format.scm
index 209c84ed1..c7565f2a1 100644
--- a/ice-9/format.scm
+++ b/ice-9/format.scm
@@ -973,7 +973,7 @@
 		(commawidth (format:par pars l 3 3 "commawidth")))
 	    (if mincol
 		(let ((numlen numstr-len)) ; calc. the output len of number
-		  (if (and (memq modifier '(at colon-at)) (> number 0))
+		  (if (and (memq modifier '(at colon-at)) (>= number 0))
 		      (set! numlen (+ numlen 1)))
 		  (if (memq modifier '(colon colon-at))
 		      (set! numlen (+ (quotient (- numstr-len 
@@ -983,7 +983,7 @@
 		  (if (> mincol numlen)
 		      (format:out-fill (- mincol numlen) padchar))))
 	    (if (and (memq modifier '(at colon-at))
-		     (> number 0))
+		     (>= number 0))
 		(format:out-char #\+))
 	    (if (memq modifier '(colon colon-at)) ; insert comma character
 		(let ((start (remainder numstr-len commawidth))