diff --git a/NEWS.md b/NEWS.md
index 588ae62b..b99a0846 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -32,6 +32,7 @@
   can be set to FALSE to recover the old version of the plot. (#171, #235,
   @ecoronado92)
 
+* Fix error in `mcmc_acf()` for some input types. (#244, #245, @hhau)
 
 # bayesplot 1.7.2
 
diff --git a/R/mcmc-diagnostics.R b/R/mcmc-diagnostics.R
index 32db0b64..d2c65560 100644
--- a/R/mcmc-diagnostics.R
+++ b/R/mcmc-diagnostics.R
@@ -580,8 +580,7 @@ acf_data <- function(x, lags) {
     abort(paste0("Too few iterations for lags=", lags, "."))
   }
 
-  data <- reshape2::melt(x, value.name = "Value")
-  data$Chain <- factor(data$Chain)
+  data <- melt_mcmc(x)
   ac_list <- tapply(
     data[["Value"]],
     # INDEX = list(data[["Chain"]], data[["Parameter"]]),