diff --git a/conformance/BUILD b/conformance/BUILD
index ce8ee59e7..5d8fe7e7a 100644
--- a/conformance/BUILD
+++ b/conformance/BUILD
@@ -136,9 +136,6 @@ cc_binary(
             "--skip_test=fields/qualified_identifier_resolution/map_field_select",
             "--skip_test=fields/qualified_identifier_resolution/ident_with_longest_prefix_check",
             # New conformance tests awaiting synchronization.
-            "--skip_test=basic/self_eval_nonzeroish/self_eval_int_hex",
-            "--skip_test=basic/self_eval_nonzeroish/self_eval_int_hex_negative",
-            "--skip_test=basic/self_eval_nonzeroish/self_eval_uint_hex",
             "--skip_test=basic/functions/unbound",
             "--skip_test=basic/functions/unbound_is_runtime_error",
             "--skip_test=comparisons/eq_literal/not_eq_list_false_vs_types",
diff --git a/parser/parser_test.cc b/parser/parser_test.cc
index 62fb88861..d06899da2 100644
--- a/parser/parser_test.cc
+++ b/parser/parser_test.cc
@@ -138,6 +138,9 @@ std::vector<TestInfo> test_cases = {
     {"0u", "0u^#1:uint64#"},
     {"23u", "23u^#1:uint64#"},
     {"24u", "24u^#1:uint64#"},
+    {"0xAu", "10u^#1:uint64#"},
+    {"-0xA", "-10^#1:int64#"},
+    {"0xA", "10^#1:int64#"},
     {"-1", "-1^#1:int64#"},
     {"4--4",
      "_-_(\n"
diff --git a/parser/visitor.cc b/parser/visitor.cc
index 7ba3a0917..037d6b4b6 100644
--- a/parser/visitor.cc
+++ b/parser/visitor.cc
@@ -7,6 +7,7 @@
 #include "absl/strings/numbers.h"
 #include "absl/strings/str_format.h"
 #include "absl/strings/str_join.h"
+#include "absl/strings/match.h"
 #include "common/escaping.h"
 #include "common/operators.h"
 #include "parser/balancer.h"
@@ -400,9 +401,13 @@ antlrcpp::Any ParserVisitor::visitInt(CelParser::IntContext* ctx) {
   if (ctx->sign) {
     value = ctx->sign->getText();
   }
+  int base = 10;
+  if (absl::StartsWith(ctx->tok->getText(), "0x")) {
+    base = 16;
+  }
   value += ctx->tok->getText();
   int64_t int_value;
-  if (absl::SimpleAtoi(value, &int_value)) {
+  if (absl::numbers_internal::safe_strto64_base(value, &int_value, base)) {
     return sf_->newLiteralInt(ctx, int_value);
   } else {
     return sf_->reportError(ctx, "invalid int literal");
@@ -415,8 +420,12 @@ antlrcpp::Any ParserVisitor::visitUint(CelParser::UintContext* ctx) {
   if (!value.empty()) {
     value.resize(value.size() - 1);
   }
+  int base = 10;
+  if (absl::StartsWith(value, "0x")) {
+    base = 16;
+  }
   uint64_t uint_value;
-  if (absl::SimpleAtoi(value, &uint_value)) {
+  if (absl::numbers_internal::safe_strtou64_base(value, &uint_value, base)) {
     return sf_->newLiteralUint(ctx, uint_value);
   } else {
     return sf_->reportError(ctx, "invalid uint literal");