diff --git a/DESCRIPTION b/DESCRIPTION
index 5015e87b..be61564e 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -34,7 +34,6 @@ Imports:
     rlang,
     rstan,
     scales,
-    voi (>= 1.0.1)
 Depends:
     R (>= 3.5.0)
 Suggests:
@@ -51,6 +50,7 @@ Suggests:
     splancs,
     testthat (>= 2.1.0),
     vdiffr,
+    voi (>= 1.0.1),
     withr
 RdMacros: Rdpack
 VignetteBuilder: knitr
diff --git a/NAMESPACE b/NAMESPACE
index 67fcab31..799589d8 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -157,4 +157,3 @@ importFrom(utils,methods)
 importFrom(utils,modifyList)
 importFrom(utils,str)
 importFrom(utils,tail)
-importFrom(voi,evppi)
diff --git a/R/evppi.default.R b/R/evppi.default.R
index dcab8566..32484451 100644
--- a/R/evppi.default.R
+++ b/R/evppi.default.R
@@ -9,7 +9,6 @@ evppi.default <- function(he, ...) {
 
 #' @rdname evppi
 #'
-#' @importFrom voi evppi
 #' @examples
 #' data(Vaccine, package = "BCEA")
 #' treats <- c("Status quo", "Vaccination")
@@ -26,6 +25,13 @@ evppi.bcea <- function(he,
                        residuals = TRUE,
                        method = NULL, ...) {
   
+  if (!requireNamespace("voi", quietly = TRUE)) {
+    stop(
+      "Package \"voi (>= 1.0.1)\" must be installed to use this function.",
+      call. = FALSE
+    )
+  }
+  
   comp_ids <- c(he$comp, he$ref)
   outputs <- list(e = he$e[, comp_ids],
                   c = he$c[, comp_ids],
diff --git a/tests/testthat/test-evppi.R b/tests/testthat/test-evppi.R
index 2e185d13..17cb17a7 100644
--- a/tests/testthat/test-evppi.R
+++ b/tests/testthat/test-evppi.R
@@ -7,6 +7,12 @@
 # library(BCEA)
 if (interactive()) library(testthat)
 
+if (!requireNamespace("voi", quietly = TRUE)) {
+  stop(
+    "Package \"voi (>= 1.0.1)\" must be installed to use this function.",
+    call. = FALSE
+  )
+}
 
 test_that("GAM regression (default) with vaccine data", {