diff --git a/R/BiomeHorizon.R b/R/BiomeHorizon.R
index e7b9860..35d92e0 100644
--- a/R/BiomeHorizon.R
+++ b/R/BiomeHorizon.R
@@ -852,7 +852,7 @@ horizonplot <- function(parameterList, aesthetics=horizonaes()) {
       for(n in (-1*nbands+1):(nbands-1)) {
         bands <- bands + (nums > n*bt)
       }
-      bands <- bands-nbands
+      bands <- as.numeric(bands-nbands)
 
       x <- numeric()
       y <- numeric()