diff --git a/NEWS.md b/NEWS.md
index 8f50d27f..1cf497be 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # readr (development version)
 
+* Invalid date formats no longer can potentially crash R (#1151)
+
 # readr 1.4.0
 
 ## Breaking changes
diff --git a/src/DateTimeParser.h b/src/DateTimeParser.h
index fdd38621..b0f22af3 100644
--- a/src/DateTimeParser.h
+++ b/src/DateTimeParser.h
@@ -285,7 +285,7 @@ class DateTimeParser {
         break;
 
       default:
-        cpp11::stop("Unsupported format %%%s", *formatItr);
+        cpp11::stop("Unsupported format %%%s", formatItr);
       }
     }
 
diff --git a/tests/testthat/test-parsing-datetime.R b/tests/testthat/test-parsing-datetime.R
index 2863a8cd..b78987e2 100644
--- a/tests/testthat/test-parsing-datetime.R
+++ b/tests/testthat/test-parsing-datetime.R
@@ -263,3 +263,7 @@ test_that("must have either two - or none", {
   expect_equal(guess_parser("200010-10"), "character")
   expect_equal(guess_parser("20001010"), "double")
 })
+
+test_that("Invalid formats error", {
+  expect_error(parse_date("2020-11-17", "%%Y-%m-%d"), "Unsupported format %%Y-%m-%d")
+})