diff --git a/R/eval_forecasts_binary.R b/R/eval_forecasts_binary.R
index 9b94d6bb0..93d7cb21b 100644
--- a/R/eval_forecasts_binary.R
+++ b/R/eval_forecasts_binary.R
@@ -45,6 +45,8 @@ eval_forecasts_binary <- function(data,
                by = summarise_by]
 
   }
+
+  return(res[])
 }
 
 
diff --git a/R/eval_forecasts_continuous_integer.R b/R/eval_forecasts_continuous_integer.R
index 34ada6c5a..82e130e12 100644
--- a/R/eval_forecasts_continuous_integer.R
+++ b/R/eval_forecasts_continuous_integer.R
@@ -169,5 +169,5 @@ eval_forecasts_sample <- function(data,
                 pit_plots = pit_histograms)
   }
 
-  return(res)
+  return(res[])
 }
diff --git a/R/eval_forecasts_helper.R b/R/eval_forecasts_helper.R
index f66bf6b4a..40088b0e0 100644
--- a/R/eval_forecasts_helper.R
+++ b/R/eval_forecasts_helper.R
@@ -20,7 +20,7 @@ add_quantiles <- function(dt, varnames, quantiles, by) {
                                                              na.rm = TRUE)),
        by = c(by)]
   }
-  return(dt)
+  return(dt[])
 }
 
 
@@ -41,5 +41,5 @@ add_sd <- function(dt, varnames, by) {
   for (varname in varnames) {
     dt[, paste0(varname, "_sd") := sd(get(varname), na.rm = TRUE), by = by]
   }
-  return(dt)
+  return(dt[])
 }
diff --git a/R/eval_forecasts_quantile.R b/R/eval_forecasts_quantile.R
index 745aff1e1..036b97ea1 100644
--- a/R/eval_forecasts_quantile.R
+++ b/R/eval_forecasts_quantile.R
@@ -194,5 +194,5 @@ eval_forecasts_quantile <- function(data,
     res[, c("quantile_coverage") := NULL]
   }
 
-  return(res)
+  return(res[])
 }