diff --git a/R/Histo2Hindcast.R b/R/Histo2Hindcast.R
index 95112f78b740682332ef1a9a1a89b20488e85639..649b75bb6349497bbe4247ef72dbc746d33aa803 100644
--- a/R/Histo2Hindcast.R
+++ b/R/Histo2Hindcast.R
@@ -130,6 +130,11 @@ Histo2Hindcast <- function(data, sdatesin, sdatesout, nleadtimesout,
     stop("Parameter 'sdatesout' must be a vector of character in the ",
          "format 'YYYYMMDD' or 'YYYYMM'. Found certain month is over 12.")
   }
+  if (any((yrout - yrin) * 12 + (mthout - mthin) < 0)) {
+    warning("Some of the start dates requested in 'sdatesout' are ",
+            "earlier than the original start date 'sdatesin'. These ",
+            "sdates will be filled with NA values")
+  }
 
   res <- Apply(data, 
                target_dims = c(sdate_dim, ftime_dim), 
@@ -151,11 +156,13 @@ Histo2Hindcast <- function(data, sdatesin, sdatesout, nleadtimesout,
 
   diff_mth <- (yrout - yrin) * 12 + (mthout - mthin)
   for (i in seq_along(diff_mth)) {
-    if (diff_mth[i] < dim(data)[2]) {
-      ftime_ind <- max(1 + diff_mth[i], 1):min(nleadtimesout + diff_mth[i], dim(data)[2])
+    ftime_ind <- max(1 + diff_mth[i], 1):min(nleadtimesout + diff_mth[i], dim(data)[2])
+    if (diff_mth[i] < 0) {
+      # Fill with NA values if the requested date is earlier than available data
+      res[i, seq_along(ftime_ind)] <- rep(NA, length(seq_along(ftime_ind)))
+    } else if (diff_mth[i] < dim(data)[2]) {
       res[i, seq_along(ftime_ind)] <- data[1, ftime_ind]
     }
   }
-  
   return(res)
 }