diff --git a/springdoc-openapi-common/src/main/java/org/springdoc/core/OpenAPIService.java b/springdoc-openapi-common/src/main/java/org/springdoc/core/OpenAPIService.java
index 9470a78d2..bec01a774 100644
--- a/springdoc-openapi-common/src/main/java/org/springdoc/core/OpenAPIService.java
+++ b/springdoc-openapi-common/src/main/java/org/springdoc/core/OpenAPIService.java
@@ -729,7 +729,7 @@ public Map<String, Object> getControllerAdviceMap() {
 	 * @return the cached open api
 	 */
 	public OpenAPI getCachedOpenAPI(Locale locale) {
-		return cachedOpenAPI.get(locale.getLanguage());
+		return cachedOpenAPI.get(locale.toLanguageTag());
 	}
 
 	/**
@@ -739,7 +739,7 @@ public OpenAPI getCachedOpenAPI(Locale locale) {
 	 * @param cachedOpenAPI the cached open api
 	 */
 	public void setCachedOpenAPI(OpenAPI cachedOpenAPI, Locale locale) {
-		this.cachedOpenAPI.put(locale.getLanguage(), cachedOpenAPI);
+		this.cachedOpenAPI.put(locale.toLanguageTag(), cachedOpenAPI);
 	}
 
 	/**
diff --git a/springdoc-openapi-webmvc-core/src/test/java/test/org/springdoc/api/app171/SpringDocApp171Test.java b/springdoc-openapi-webmvc-core/src/test/java/test/org/springdoc/api/app171/SpringDocApp171Test.java
index 59a505446..9c6394d9a 100644
--- a/springdoc-openapi-webmvc-core/src/test/java/test/org/springdoc/api/app171/SpringDocApp171Test.java
+++ b/springdoc-openapi-webmvc-core/src/test/java/test/org/springdoc/api/app171/SpringDocApp171Test.java
@@ -48,6 +48,7 @@ public void testApp() throws Exception {
 		Locale.setDefault(Locale.US);
 		testApp(Locale.US);
 		testApp(Locale.FRANCE);
+		testApp(Locale.UK);
 	}
 
 	private void testApp(Locale locale) throws Exception {
@@ -57,7 +58,7 @@ private void testApp(Locale locale) throws Exception {
 				mockMvc.perform(get(Constants.DEFAULT_API_DOCS_URL).locale(locale).header(HttpHeaders.ACCEPT_LANGUAGE, locale.toLanguageTag())).andExpect(status().isOk())
 						.andExpect(jsonPath("$.openapi", is("3.0.1"))).andReturn();
 		String result = mockMvcResult.getResponse().getContentAsString();
-		String expected = getContent("results/app" + testNumber + "-" + locale.getLanguage() + ".json");
+		String expected = getContent("results/app" + testNumber + "-" + locale.toLanguageTag() + ".json");
 		assertEquals(expected, result, true);
 	}
 }
\ No newline at end of file
diff --git a/springdoc-openapi-webmvc-core/src/test/resources/messages_en_GB.properties b/springdoc-openapi-webmvc-core/src/test/resources/messages_en_GB.properties
new file mode 100644
index 000000000..408cbad44
--- /dev/null
+++ b/springdoc-openapi-webmvc-core/src/test/resources/messages_en_GB.properties
@@ -0,0 +1,6 @@
+greeting=Hello! Welcome to our website![EN_GB]
+lang.change=Change the language[EN_GB]
+lang.eng=English[EN_GB]
+lang.fr=French[EN_GB]
+mySample=toto[EN_GB]
+test=This is a test message[EN_GB]
\ No newline at end of file
diff --git a/springdoc-openapi-webmvc-core/src/test/resources/results/app171-en-GB.json b/springdoc-openapi-webmvc-core/src/test/resources/results/app171-en-GB.json
new file mode 100644
index 000000000..0f4cf0cc0
--- /dev/null
+++ b/springdoc-openapi-webmvc-core/src/test/resources/results/app171-en-GB.json
@@ -0,0 +1,65 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "OpenAPI definition",
+    "version": "v0"
+  },
+  "servers": [
+    {
+      "url": "http://localhost",
+      "description": "Generated server url"
+    }
+  ],
+  "tags": [
+    {
+      "name": "Hello! Welcome to our website![EN_GB]",
+      "description": "This is a test message[EN_GB]"
+    }
+  ],
+  "paths": {
+    "/test": {
+      "get": {
+        "tags": [
+          "Hello! Welcome to our website![EN_GB]"
+        ],
+        "operationId": "demo2",
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "*/*": {
+                "schema": {
+                  "type": "string"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
+    "/persons": {
+      "get": {
+        "tags": [
+          "Hello! Welcome to our website![EN_GB]"
+        ],
+        "operationId": "persons",
+        "parameters": [
+          {
+            "name": "name",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK"
+          }
+        }
+      }
+    }
+  },
+  "components": {}
+}
diff --git a/springdoc-openapi-webmvc-core/src/test/resources/results/app171-en.json b/springdoc-openapi-webmvc-core/src/test/resources/results/app171-en-US.json
similarity index 100%
rename from springdoc-openapi-webmvc-core/src/test/resources/results/app171-en.json
rename to springdoc-openapi-webmvc-core/src/test/resources/results/app171-en-US.json
diff --git a/springdoc-openapi-webmvc-core/src/test/resources/results/app171-fr.json b/springdoc-openapi-webmvc-core/src/test/resources/results/app171-fr-FR.json
similarity index 100%
rename from springdoc-openapi-webmvc-core/src/test/resources/results/app171-fr.json
rename to springdoc-openapi-webmvc-core/src/test/resources/results/app171-fr-FR.json