diff --git a/src/integer64.c b/src/integer64.c
index 7c0bbd0..5fccac2 100644
--- a/src/integer64.c
+++ b/src/integer64.c
@@ -156,7 +156,17 @@ SEXP as_integer64_character(SEXP x_, SEXP ret_){
   char * endpointer;
   for(i=0; i<n; i++){
     str = CHAR(STRING_ELT(x_, i)); endpointer = (char *)str; // thanks to Murray Stokely 28.1.2012
-    ret[i] = strtoll(str, &endpointer, 10);
+    int base = 10; // default
+    int sign = 1;  // default 
+    if (str[0]=='-'){
+      sign = -1;
+      str++;
+    }
+    if (str[0]=='0' && (str[1] == 'x' || str[1] == 'X')){
+        base = 16;
+        str += 2;
+    }
+    ret[i] = strtoll(str, &endpointer, base) * sign;
     if (*endpointer)
       ret[i] = NA_INTEGER64;
   }
diff --git a/tests/testthat/test-integer64.R b/tests/testthat/test-integer64.R
index 838a711..aa4050b 100644
--- a/tests/testthat/test-integer64.R
+++ b/tests/testthat/test-integer64.R
@@ -8,8 +8,8 @@ test_that("integer64 coercion to/from other types work", {
 
   # to integer64
   expect_identical(as.integer64(TRUE), as.integer64(1L))
-  expect_identical(as.integer64(as.character(1:10)), as.integer64(1:10))
-  expect_identical(as.integer64(as.double(1:10)), as.integer64(1:10))
+  expect_identical(as.integer64(as.character(-10:10)), as.integer64(-10:10))
+  expect_identical(as.integer64(as.double(-10:10)), as.integer64(-10:10))
   expect_identical(as.integer64(NULL), as.integer64())
   x = as.integer64(1:10)
   expect_identical(as.integer64(x), x)
@@ -29,6 +29,24 @@ test_that("integer64 coercion to/from other types work", {
   expect_identical(as.integer64(NA_character_), NA_integer64_)
 })
 
+test_that("hex string --> integer64 coercion works (as it does for integer)", {
+  expect_identical(as.integer64(c("0x1", "0xF")), as.integer64(c(1L, 15L)))
+  # Test the first value too large to store in a 32-bit signed integer.
+  expect_identical(as.integer64("0x100000000"), as.integer64(2L^32L))
+  # Test some negative values.
+  expect_identical(as.integer64(c("-0x0", "-0x1", "-0xF")), as.integer64(c(0L, -1L, -15L)))
+  # Test mixed positive and negatives
+  expect_identical(as.integer64(c("-0xA", "0xF")), as.integer64(c(-10L, 15L)))
+  # Test the smallest and largest values different from the extreme values of the representation.
+  expect_identical(as.integer64(c("-0x7FFFFFFFFFFFFFFE", "0x7FFFFFFFFFFFFFFE")), lim.integer64() + c(1L, -1L))
+  # Test smallest and largest representable values.
+  expect_identical(as.integer64(c("-0x7FFFFFFFFFFFFFFF", "0x7FFFFFFFFFFFFFFF")), lim.integer64())
+  # not representable in 64 bits --> lim.integer64(), same as non-hex string input
+  expect_identical(as.integer64(c("-0x8000000000000000", "0x8000000000000000")), lim.integer64())
+  # case insensitive
+  expect_identical(as.integer64(c("0xa", "0Xa", "0xA", "0xa")), as.integer64(rep(10L, 4L)))
+})
+
 test_that("S3 class basics work", {
   x = as.integer64(1:10)
   expect_s3_class(x, "integer64")