diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index 25a64d6486..9dabecfd93 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -128,7 +128,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     // first n-1 elements
@@ -201,7 +202,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     // first n-1 elements
@@ -262,7 +264,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     o->write_characters(indent_string.c_str(), new_indent);
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 2e16ad5b9e..662c9afb0a 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -19302,7 +19302,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     // first n-1 elements
@@ -19375,7 +19376,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     // first n-1 elements
@@ -19436,7 +19438,8 @@ class serializer
                     const auto new_indent = current_indent + indent_step;
                     if (JSON_HEDLEY_UNLIKELY(indent_string.size() < new_indent))
                     {
-                        indent_string.resize(indent_string.size() * 2, ' ');
+                        indent_string.resize((std::max)(indent_string.size() * 2, static_cast<std::size_t>(new_indent)), indent_char);
+                        JSON_ASSERT(indent_string.size() >= new_indent);
                     }
 
                     o->write_characters(indent_string.c_str(), new_indent);
diff --git a/tests/src/unit-inspection.cpp b/tests/src/unit-inspection.cpp
index c70913d5b1..d79764bffd 100644
--- a/tests/src/unit-inspection.cpp
+++ b/tests/src/unit-inspection.cpp
@@ -245,6 +245,41 @@ TEST_CASE("object inspection")
             CHECK(binary.dump(1024).size() == 2086);
         }
 
+        SECTION("indentation and resize")
+        {
+            SECTION("array")
+            {
+                const auto j_array = json::parse("[[[[[[]]]]]]");
+                // check right size after indentation triggering a resize
+                CHECK(j_array.dump(1024).size() == 25622);
+                // check if right indentation symbol is used
+                CHECK(j_array.dump(1024, '\t')[4096] == '\t');
+                // check resize is large enough
+                CHECK(j_array.dump(10000).size() == 250022);
+            }
+
+            SECTION("object")
+            {
+                const auto j_object = json::parse(R"({"":{"":{"":{"":{"":{}}}}}})");
+                // check right size after indentation triggering a resize
+                CHECK(j_object.dump(1024).size() == 25642);
+                // check if right indentation symbol is used
+                CHECK(j_object.dump(1024, '\t')[4096] == '\t');
+                // check resize is large enough
+                CHECK(j_object.dump(10000).size() == 250042);
+            }
+
+            SECTION("binary")
+            {
+                const auto j_binary = json::binary({1, 2, 3}, 128);
+                // check right size after indentation triggering a resize
+                CHECK(j_binary.dump(1024).size() == 2086);
+                CHECK(j_binary.dump(1024, '\t')[1024] == '\t');
+                // check resize is large enough
+                CHECK(j_binary.dump(10000).size() == 20038);
+            }
+        }
+
         SECTION("dump and floating-point numbers")
         {
             auto s = json(42.23).dump();