diff --git a/R/MovingAverages.R b/R/MovingAverages.R
index 9e0c909..9e5276f 100755
--- a/R/MovingAverages.R
+++ b/R/MovingAverages.R
@@ -51,6 +51,11 @@ function (x, n=10, wilder=FALSE, ratio=NULL) {
   # Check for non-leading NAs
   # Leading NAs are handled in the C code
   x.na <- xts:::naCheck(x, n)
+  
+  # If ratio is specified, and n is not, set n to approx 'correct'
+  # value backed out from ratio
+  if(missing(n) && !missing(ratio))
+    n <- trunc(2/ratio - 1)
 
   # Determine decay ratio
   if(is.null(ratio)) {