diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumClass.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumClass.mustache
index cb8539bd10e..7cead92c539 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumClass.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumClass.mustache
@@ -77,7 +77,7 @@
                     return b;
                 }
             }
-            {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/isNullable}}
+            {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}{{#enumUnknownDefaultCase}}{{#allowableValues}}{{#enumVars}}{{#-last}}return {{{name}}};{{/-last}}{{/enumVars}}{{/allowableValues}}{{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/enumUnknownDefaultCase}}{{/isNullable}}
         }
     {{/jackson}}
     {{/withXml}}
diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumOuterClass.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumOuterClass.mustache
index 2539064d171..588e52c7e31 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumOuterClass.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/microprofile/enumOuterClass.mustache
@@ -65,6 +65,6 @@ import java.net.URI;
         return b;
       }
     }
-    {{#useNullForUnknownEnumValue}}return null;{{/useNullForUnknownEnumValue}}{{^useNullForUnknownEnumValue}}throw new IllegalArgumentException("Unexpected value '" + text + "'");{{/useNullForUnknownEnumValue}}
+    {{#useNullForUnknownEnumValue}}return null;{{/useNullForUnknownEnumValue}}{{^useNullForUnknownEnumValue}}{{#enumUnknownDefaultCase}}{{#allowableValues}}{{#enumVars}}{{#-last}}return {{{name}}};{{/-last}}{{/enumVars}}{{/allowableValues}}{{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}throw new IllegalArgumentException("Unexpected value '" + text + "'");{{/enumUnknownDefaultCase}}{{/useNullForUnknownEnumValue}}
   }
 }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java
new file mode 100644
index 00000000000..41ae57b52bb
--- /dev/null
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java
@@ -0,0 +1,75 @@
+package org.openapitools.codegen.java.microprofile;
+
+import io.swagger.parser.OpenAPIParser;
+import io.swagger.v3.oas.models.OpenAPI;
+import io.swagger.v3.parser.core.models.ParseOptions;
+import org.openapitools.codegen.ClientOptInput;
+import org.openapitools.codegen.CodegenConstants;
+import org.openapitools.codegen.DefaultGenerator;
+import org.openapitools.codegen.java.assertions.JavaFileAssert;
+import org.openapitools.codegen.languages.JavaMicroprofileServerCodegen;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class JavaMicroprofileServerCodegenTest {
+
+    protected JavaMicroprofileServerCodegen codegen;
+
+    @BeforeMethod
+    public void before() {
+        codegen = new JavaMicroprofileServerCodegen();
+    }
+
+    @Test
+    public void testEnumUnknownDefaultCaseDeserializationTrue_issue19674() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/bugs/issue_19674.yaml", null, new ParseOptions()).getOpenAPI();
+
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(CodegenConstants.ENUM_UNKNOWN_DEFAULT_CASE, "true");
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert.assertThat(files.get("Color.java"))
+                .assertMethod("fromValue").bodyContainsLines("return UNKNOWN_DEFAULT_OPEN_API");
+
+    }
+
+    @Test
+    public void testEnumUnknownDefaultCaseDeserializationNotSet_issue19674() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/bugs/issue_19674.yaml", null, new ParseOptions()).getOpenAPI();
+
+        codegen.setOutputDir(output.getAbsolutePath());
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert.assertThat(files.get("Color.java"))
+                .assertMethod("fromValue").bodyContainsLines("throw new IllegalArgumentException(\"Unexpected value '\" + text + \"'\");");
+
+    }
+}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/bugs/issue_19674.yaml b/modules/openapi-generator/src/test/resources/bugs/issue_19674.yaml
new file mode 100644
index 00000000000..b30b61f1918
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/bugs/issue_19674.yaml
@@ -0,0 +1,17 @@
+openapi: "3.0.0"
+info:
+  version: 2.0.0
+  title: test
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      responses:
+        '200':
+          description: OK
+components:
+  schemas:
+    Color:
+      type: string
+      enum: [RED, BLUE, GREEN]
\ No newline at end of file