diff --git a/R/R/prophet.R b/R/R/prophet.R
index 337a349..ead91ea 100644
--- a/R/R/prophet.R
+++ b/R/R/prophet.R
@@ -393,6 +393,9 @@ setup_dataframe <- function(m, df, initialize_scales = FALSE) {
     if (!(exists('cap', where=df))) {
       stop('Capacities must be supplied for logistic growth.')
     }
+    if (any(df$cap <= df$floor)) {
+      stop('cap must be greater than floor (which defaults to 0).')
+    }
     df <- df %>%
       dplyr::mutate(cap_scaled = (cap - floor) / m$y.scale)
   }
diff --git a/python/fbprophet/forecaster.py b/python/fbprophet/forecaster.py
index d8096ca..2433dec 100644
--- a/python/fbprophet/forecaster.py
+++ b/python/fbprophet/forecaster.py
@@ -274,6 +274,10 @@ class Prophet(object):
                     "Capacities must be supplied for logistic growth in "
                     "column 'cap'"
                 )
+            if (df['cap'] <= df['floor']).any():
+                raise ValueError(
+                    'cap must be greater than floor (which defaults to 0).'
+                )
             df['cap_scaled'] = (df['cap'] - df['floor']) / self.y_scale
 
         df['t'] = (df['ds'] - self.start) / self.t_scale