diff --git a/R/plot_emission_intensity.R b/R/plot_emission_intensity.R
index e2ffd53c..d6f8e12e 100644
--- a/R/plot_emission_intensity.R
+++ b/R/plot_emission_intensity.R
@@ -65,8 +65,16 @@ prep_emission_intensity <- function(data,
                                     convert_label = identity,
                                     span_5yr = FALSE) {
   out <- data %>%
-    prep_common() %>%
-    mutate(label = convert_label(.data$label))
+    prep_common()
+
+  if (is.factor(out$label)) {
+    out$label <- factor(
+      convert_label(out$label),
+      levels = convert_label(levels(out$label))
+      )
+  } else {
+    out$label <- convert_label(out$label)
+  }
 
   if (span_5yr) {
     out <- span_5yr(out)
diff --git a/tests/testthat/test-plot_emission_intensity.R b/tests/testthat/test-plot_emission_intensity.R
index 729f39a5..abe266cb 100644
--- a/tests/testthat/test-plot_emission_intensity.R
+++ b/tests/testthat/test-plot_emission_intensity.R
@@ -91,6 +91,88 @@ test_that("throws expected warning about API change", {
 test_that("with data with `label` column and with `scale_colour_r2dii()`,
           outputs expected labels and colours (#535)", {
 
+            skip_if(r_version_is_older_than(4))
+
+            input_levels <- c(
+              "projected",
+              "corporate_economy",
+              "target_demo",
+              "adjusted_scenario_demo"
+            )
+
+            data <- filter(sda, sector == "cement", region == "global") %>%
+              dplyr::mutate(
+                emission_factor_metric = factor(
+                  .data$emission_factor_metric,
+                  levels = input_levels
+                ),
+                label = to_title(.data$emission_factor_metric)
+              )
+
+            input_colour_scale <- c(
+              "dark_blue",
+              "green",
+              "grey",
+              "ruby_red"
+            )
+
+            expected_output <- data.frame(
+              levels = input_levels,
+              colour_name = input_colour_scale
+            ) %>%
+              left_join(palette_colours, by = c(colour_name = "label"))
+
+            p <- suppressWarnings(
+              plot_emission_intensity(data),
+              classes = "lifecycle_warning_deprecated"
+            )
+
+            p <- p + scale_colour_r2dii(
+              colour_labels = input_colour_scale,
+            )
+
+            g <- ggplot_build(p)
+
+            plot_output_labels <- g$plot$scales$scales[[3]]$get_labels()
+            plot_output_colours <- g$plot$scales$scales[[3]]$palette(
+              length(plot_output_labels)
+            )
+
+            plot_output <- data.frame(
+              labels = plot_output_labels,
+              hex = plot_output_colours
+            )
+
+            expected_output <- split(expected_output, expected_output$levels)
+            plot_output <- split(plot_output, plot_output$labels)
+
+            expect_equal(
+              expected_output$projected$hex,
+              plot_output$`Projected`$hex
+            )
+
+            expect_equal(
+              expected_output$corporate_economy$hex,
+              plot_output$`Corporate Economy`$hex
+            )
+
+            expect_equal(
+              expected_output$target_demo$hex,
+              plot_output$`Target Demo`$hex
+            )
+
+            expect_equal(
+              expected_output$adjusted_scenario_demo$hex,
+              plot_output$`Adjusted Scenario Demo`$hex
+            )
+
+          })
+
+test_that("with `convert_label = to_title`, outputs custom colour scale with
+          expected order (#536)", {
+
+  skip_if(r_version_is_older_than(4))
+
   input_levels <- c(
     "projected",
     "corporate_economy",
@@ -103,8 +185,7 @@ test_that("with data with `label` column and with `scale_colour_r2dii()`,
       emission_factor_metric = factor(
         .data$emission_factor_metric,
         levels = input_levels
-      ),
-      label = to_title(.data$emission_factor_metric)
+      )
     )
 
   input_colour_scale <- c(
@@ -120,8 +201,9 @@ test_that("with data with `label` column and with `scale_colour_r2dii()`,
   ) %>%
     left_join(palette_colours, by = c(colour_name = "label"))
 
+
   p <- suppressWarnings(
-    plot_emission_intensity(data),
+    plot_emission_intensity(data, convert_label = to_title),
     classes = "lifecycle_warning_deprecated"
   )
 
@@ -134,7 +216,7 @@ test_that("with data with `label` column and with `scale_colour_r2dii()`,
   plot_output_labels <- g$plot$scales$scales[[3]]$get_labels()
   plot_output_colours <- g$plot$scales$scales[[3]]$palette(
     length(plot_output_labels)
-    )
+  )
 
   plot_output <- data.frame(
     labels = plot_output_labels,
@@ -164,4 +246,5 @@ test_that("with data with `label` column and with `scale_colour_r2dii()`,
     plot_output$`Adjusted Scenario Demo`$hex
   )
 
+
 })