diff --git a/NEWS.md b/NEWS.md
index 2c6fba4..ba0a681 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,6 +1,7 @@
 # isopleuros 1.2.0.9000
 ## Enhancements
-* Allow to center and scale label positions.
+* Allow to center and scale label coordinates.
+* Generate diagnostic messages if coordinates are not centered/scaled when they should be.
 
 # isopleuros 1.2.0
 ## Enhancements
diff --git a/R/coordinates.R b/R/coordinates.R
index 373f81c..500b17d 100644
--- a/R/coordinates.R
+++ b/R/coordinates.R
@@ -15,6 +15,8 @@ setMethod(
     n <- length(x)
     assert_length(y, n)
     assert_length(z, n)
+    assert_center(center)
+    assert_scale(scale)
 
     ## Missing values
     if (missing) {
diff --git a/R/isopleuros-internal.R b/R/isopleuros-internal.R
index f4324fc..ec1231d 100644
--- a/R/isopleuros-internal.R
+++ b/R/isopleuros-internal.R
@@ -63,3 +63,21 @@ assert_length <- function(x, expected) {
   }
   invisible(x)
 }
+
+assert_center <- function(x, current = getOption("isopleuros.center")) {
+  ok <- isTRUE(x) || is.numeric(x)
+  if (!ok && is.numeric(current) && !all(current == 1)) {
+    msg <- "The current plot has been centered, but your data doesn't seem to be."
+    message(msg)
+  }
+  invisible(x)
+}
+
+assert_scale <- function(x, current = getOption("isopleuros.scale")) {
+  ok <- isTRUE(x) || is.numeric(x)
+  if (!ok && is.numeric(current) && !all(current == 1)) {
+    msg <- "The current plot has been scaled, but your data doesn't seem to be."
+    message(msg)
+  }
+  invisible(x)
+}
diff --git a/R/ternary_grid.R b/R/ternary_grid.R
index 5f76dbd..46825ea 100644
--- a/R/ternary_grid.R
+++ b/R/ternary_grid.R
@@ -54,8 +54,8 @@ ternary_grid <- function(primary = NULL, secondary = NULL,
     for (i in x) {
       start <- matrix(data = c(i, 0, 1 - i, 1 - i, i, 0, 0, 1 - i, i), ncol = 3)
       end <- matrix(data = c(i, 1 - i, 0, 0, i, 1 - i, 1 - i, 0, i), ncol = 3)
-      start <- coordinates_ternary(start)
-      end <- coordinates_ternary(end)
+      start <- list(x = start[, 2] + start[, 3] / 2, y = start[, 3] * sqrt(3) / 2)
+      end <- list(x = end[, 2] + end[, 3] / 2, y = end[, 3] * sqrt(3) / 2)
 
       mapply(
         FUN = function(x_from, x_to, y_from, y_to, n, center, scale) {
diff --git a/R/ternary_plot.R b/R/ternary_plot.R
index 3474629..24bf2c3 100644
--- a/R/ternary_plot.R
+++ b/R/ternary_plot.R
@@ -48,6 +48,10 @@ setMethod(
     }
     graphics::plot.window(xlim = lim$x, ylim = lim$y, asp = 1)
 
+    ## Reset center and scale
+    options(isopleuros.center = NULL)
+    options(isopleuros.scale = NULL)
+
     ## Compute ternary coordinates
     pt <- coordinates_ternary(x = x, y = y, z = z, center = center, scale = scale)
 
diff --git a/inst/tinytest/test_scale.R b/inst/tinytest/test_scale.R
index c4a7258..ea9d5b9 100644
--- a/inst/tinytest/test_scale.R
+++ b/inst/tinytest/test_scale.R
@@ -1,3 +1,15 @@
+ternary_plot(lava, center = TRUE, scale = FALSE)
+expect_message(ternary_points(lava), "The current plot has been centered")
+
+ternary_plot(lava, center = FALSE, scale = TRUE)
+expect_message(ternary_points(lava), "The current plot has been scaled")
+
+ternary_plot(lava, center = TRUE, scale = TRUE)
+expect_message(ternary_points(lava))
+
+ternary_plot(lava, center = FALSE, scale = FALSE)
+expect_silent(ternary_points(lava))
+
 if (at_home()) {
   using("tinysnapshot")
   options(tinysnapshot_device = "svglite")