diff --git a/include/nlohmann/detail/json_pointer.hpp b/include/nlohmann/detail/json_pointer.hpp
index 5e4c8a1f..421c5ec8 100644
--- a/include/nlohmann/detail/json_pointer.hpp
+++ b/include/nlohmann/detail/json_pointer.hpp
@@ -678,6 +678,27 @@ class json_pointer
                         // "-" always fails the range check
                         return false;
                     }
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 and not ("0" <= reference_token and reference_token <= "9")))
+                    {
+                        // invalid char
+                        return false;
+                    }
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() > 1))
+                    {
+                        if (JSON_HEDLEY_UNLIKELY(not ('1' <= reference_token[0] and reference_token[0] <= '9')))
+                        {
+                            // first char should be between '1' and '9'
+                            return false;
+                        }
+                        for (std::size_t i = 1; i < reference_token.size(); i++)
+                        {
+                            if (JSON_HEDLEY_UNLIKELY(not ('0' <= reference_token[i] and reference_token[i] <= '9')))
+                            {
+                                // other char should be between '0' and '9'
+                                return false;
+                            }
+                        }
+                    }
 
                     const auto idx = static_cast<size_type>(array_index(reference_token));
                     if (idx >= ptr->size())
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index e5789a48..f04091d0 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -11487,6 +11487,27 @@ class json_pointer
                         // "-" always fails the range check
                         return false;
                     }
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 and not ("0" <= reference_token and reference_token <= "9")))
+                    {
+                        // invalid char
+                        return false;
+                    }
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() > 1))
+                    {
+                        if (JSON_HEDLEY_UNLIKELY(not ('1' <= reference_token[0] and reference_token[0] <= '9')))
+                        {
+                            // first char should be between '1' and '9'
+                            return false;
+                        }
+                        for (std::size_t i = 1; i < reference_token.size(); i++)
+                        {
+                            if (JSON_HEDLEY_UNLIKELY(not ('0' <= reference_token[i] and reference_token[i] <= '9')))
+                            {
+                                // other char should be between '0' and '9'
+                                return false;
+                            }
+                        }
+                    }
 
                     const auto idx = static_cast<size_type>(array_index(reference_token));
                     if (idx >= ptr->size())
diff --git a/test/src/unit-json_pointer.cpp b/test/src/unit-json_pointer.cpp
index 1655a458..2cc9dac6 100644
--- a/test/src/unit-json_pointer.cpp
+++ b/test/src/unit-json_pointer.cpp
@@ -310,12 +310,11 @@ TEST_CASE("JSON pointers")
             CHECK_THROWS_AS(j_const.at("/01"_json_pointer), json::parse_error&);
             CHECK_THROWS_WITH(j_const.at("/01"_json_pointer),
                               "[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'");
-            CHECK_THROWS_AS(j.contains("/01"_json_pointer), json::parse_error&);
-            CHECK_THROWS_WITH(j.contains("/01"_json_pointer),
-                              "[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'");
-            CHECK_THROWS_AS(j_const.contains("/01"_json_pointer), json::parse_error&);
-            CHECK_THROWS_WITH(j_const.contains("/01"_json_pointer),
-                              "[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'");
+
+            CHECK(not j.contains("/01"_json_pointer));
+            CHECK(not j.contains("/01"_json_pointer));
+            CHECK(not j_const.contains("/01"_json_pointer));
+            CHECK(not j_const.contains("/01"_json_pointer));
 
             // error with incorrect numbers
             CHECK_THROWS_AS(j["/one"_json_pointer] = 1, json::parse_error&);
@@ -360,12 +359,10 @@ TEST_CASE("JSON pointers")
             CHECK_THROWS_WITH(j_const.at("/one"_json_pointer) == 1,
                               "[json.exception.parse_error.109] parse error: array index 'one' is not a number");
 
-            CHECK_THROWS_AS(j.contains("/one"_json_pointer), json::parse_error&);
-            CHECK_THROWS_WITH(j.contains("/one"_json_pointer),
-                              "[json.exception.parse_error.109] parse error: array index 'one' is not a number");
-            CHECK_THROWS_AS(j_const.contains("/one"_json_pointer), json::parse_error&);
-            CHECK_THROWS_WITH(j_const.contains("/one"_json_pointer),
-                              "[json.exception.parse_error.109] parse error: array index 'one' is not a number");
+            CHECK(not j.contains("/one"_json_pointer));
+            CHECK(not j.contains("/one"_json_pointer));
+            CHECK(not j_const.contains("/one"_json_pointer));
+            CHECK(not j_const.contains("/one"_json_pointer));
 
             CHECK_THROWS_AS(json({{"/list/0", 1}, {"/list/1", 2}, {"/list/three", 3}}).unflatten(), json::parse_error&);
             CHECK_THROWS_WITH(json({{"/list/0", 1}, {"/list/1", 2}, {"/list/three", 3}}).unflatten(),