diff --git a/tests/testthat/test-bigmemory.R b/tests/testthat/test-bigmemory.R
index 833c418..e7cb440 100644
--- a/tests/testthat/test-bigmemory.R
+++ b/tests/testthat/test-bigmemory.R
@@ -11,14 +11,14 @@ test_that("Conversion to big.matrix works", {
   for (t in c("raw", "integer", "float", "double")) {
 
     X <- FBM(10, 10, type = t, init = 0)
-    if (t != "raw") X[1] <- NA
+    if (t != "raw") X[1, 1] <- NA
 
     # Conversion works
     expect_s4_class(X$bm.desc(), "big.matrix.descriptor")
     expect_s4_class(X2 <- X$bm(), "big.matrix")
     expect_identical(typeof(X2), typeof(X))
     if (t != "float" && not_cran)
-      expect_equal(as.numeric(X2[1]), as.numeric(X[1]))
+      expect_equal(as.numeric(X2[1, 1]), as.numeric(X[1, 1]))
 
     # Permissions
     X$is_read_only <- TRUE