diff --git a/server/src/dev/resources/application.yml b/server/src/dev/resources/application.yml
index 0ba9f1a11..c2913e9b0 100644
--- a/server/src/dev/resources/application.yml
+++ b/server/src/dev/resources/application.yml
@@ -96,6 +96,10 @@ management:
 
 springdoc:
   model-and-view-allowed: true
+  api-docs:
+    # springdoc 3.x defaults to OpenAPI 3.1, whose mapper in swagger-core writes a single schema type as
+    # a bare string but cannot read one back, so springdoc warns on every schema it tries to clone.
+    version: openapi_3_0
   swagger-ui:
     path: /swagger-ui
     docExpansion: list
diff --git a/server/src/main/java/org/eclipse/openvsx/web/DocumentationConfig.java b/server/src/main/java/org/eclipse/openvsx/web/DocumentationConfig.java
index 22954ea5b..f0dd05a32 100644
--- a/server/src/main/java/org/eclipse/openvsx/web/DocumentationConfig.java
+++ b/server/src/main/java/org/eclipse/openvsx/web/DocumentationConfig.java
@@ -17,6 +17,7 @@
 import io.swagger.v3.oas.models.headers.Header;
 import io.swagger.v3.oas.models.info.Info;
 import io.swagger.v3.oas.models.info.License;
+import io.swagger.v3.oas.models.media.IntegerSchema;
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.responses.ApiResponse;
 import io.swagger.v3.oas.models.responses.ApiResponses;
@@ -135,20 +136,26 @@ public OpenApiCustomizer sortSchemasAlphabetically() {
         };
     }
 
+    /**
+     * Schemas must be built through the typed subclasses rather than {@code new Schema<>().type(...)}.
+     * The latter only sets the legacy string {@code type}, which an OpenAPI 3.1 document does not
+     * serialize at all - springdoc 3.x emits 3.1 by default - leaving the header with no type. The
+     * typed subclasses populate both that field and the 3.1 {@code types} set.
+     */
     @Bean
     public OpenApiCustomizer addRateLimitResponse() {
         var limitLimitHeader = new Header()
                 .description("Number of requests that can be made in a given amount of time")
-                .schema(new Schema<>().type("integer").format("int32"));
+                .schema(new IntegerSchema().format("int32"));
         var limitRemainingHeader = new Header()
                 .description("Remaining number of requests left in the current time window")
-                .schema(new Schema<>().type("integer").format("int32"));
+                .schema(new IntegerSchema().format("int32"));
         var limitResetHeader = new Header()
                 .description("Number of seconds until the rate limit tokens will be fully filled to its maximum")
-                .schema(new Schema<>().type("integer").format("int32"));
+                .schema(new IntegerSchema().format("int32"));
         var retryAfterHeader = new Header()
                 .description("Number of seconds to wait after receiving a 429 response")
-                .schema(new Schema<>().type("integer").format("int32"));
+                .schema(new IntegerSchema().format("int32"));
 
         var response = new ApiResponse()
                 .description("A client has sent too many requests in a given amount of time")
diff --git a/server/src/test/java/org/eclipse/openvsx/web/DocumentationConfigTest.java b/server/src/test/java/org/eclipse/openvsx/web/DocumentationConfigTest.java
index bd7ff1a16..b0dbead37 100644
--- a/server/src/test/java/org/eclipse/openvsx/web/DocumentationConfigTest.java
+++ b/server/src/test/java/org/eclipse/openvsx/web/DocumentationConfigTest.java
@@ -14,7 +14,12 @@
 
 import java.lang.reflect.Method;
 
+import io.swagger.v3.core.util.Json;
+import io.swagger.v3.core.util.Json31;
+import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
+import io.swagger.v3.oas.models.PathItem;
+import io.swagger.v3.oas.models.Paths;
 import org.junit.jupiter.api.Test;
 import org.springframework.web.method.HandlerMethod;
 
@@ -59,6 +64,29 @@ void shouldMarkAPreviewOperationOnlyOnce() {
         assertThat(operation.getDescription()).containsOnlyOnce("**Preview**");
     }
 
+    // springdoc 3.x emits OpenAPI 3.1 by default, which does not serialize the legacy string `type` a
+    // bare `new Schema<>().type(...)` sets - the header then documents no type at all. The rate limit
+    // headers have to survive both spec versions, since which one is emitted is a springdoc default.
+    @Test
+    void shouldGiveTheRateLimitHeadersATypeInEitherSpecVersion() throws Exception {
+        var openApi = new OpenAPI().paths(
+                new Paths().addPathItem("/api/-/search", new PathItem().get(new Operation())));
+
+        new DocumentationConfig().addRateLimitResponse().customise(openApi);
+
+        var schema = openApi.getPaths()
+                .get("/api/-/search")
+                .getGet()
+                .getResponses()
+                .get("429")
+                .getHeaders()
+                .get("X-RateLimit-Limit")
+                .getSchema();
+
+        assertThat(Json.mapper().writeValueAsString(schema)).contains("\"type\":\"integer\"");
+        assertThat(Json31.mapper().writeValueAsString(schema)).contains("\"type\":\"integer\"");
+    }
+
     private void customize(Operation operation, String methodName) {
         Method method;
         try {