diff --git a/doc/guide.md b/doc/guide.md
index 4d46c9630..fb83851d0 100644
--- a/doc/guide.md
+++ b/doc/guide.md
@@ -1100,6 +1100,11 @@ posted.
 Note that Okapi gives us less details about the modules, for in the real life this
 could be quite a long list.
 
+Modules are immutable (for same id). There is no PUT method to update a module.
+It is possible to POST the module descriptor again, if it is equivalent to the
+existing module. This enforcement can be lifted, by supplying query
+parameter `check=false`.
+
 #### Deploying the module
 
 It is not enough that Okapi knows that such a module exists. We must
diff --git a/okapi-core/src/main/java/org/folio/okapi/managers/ModuleManager.java b/okapi-core/src/main/java/org/folio/okapi/managers/ModuleManager.java
index 757e6243c..f37870b38 100644
--- a/okapi-core/src/main/java/org/folio/okapi/managers/ModuleManager.java
+++ b/okapi-core/src/main/java/org/folio/okapi/managers/ModuleManager.java
@@ -78,7 +78,7 @@ private Future<Void> loadModules() {
    * Create a list of modules.
    *
    * @param list list of modules
-   * @param check whether to check dependencies
+   * @param check whether to check dependencies and immutability of existing modules
    * @param removeIfMissingDep skip modules where dependency check fails
    * @return future
    */
@@ -91,7 +91,7 @@ public Future<Void> createList(List<ModuleDescriptor> list, boolean check,
    * Create a list of modules.
    *
    * @param list list of modules
-   * @param check whether to check dependencies
+   * @param check whether to check dependencies and immutability of existing modules
    * @param moduleVersionFilter whether to allow pre-release/npmSnapshots
    * @param removeIfMissingDep skip modules where dependency check fails
    * @return future
@@ -110,7 +110,7 @@ public Future<Void> createList(List<ModuleDescriptor> list, boolean check,
           ModuleDescriptor exMd = tempList.get(id);
           String exJson = Json.encodePrettily(exMd);
           String json = Json.encodePrettily(md);
-          if (!json.equals(exJson)) {
+          if (check && !json.equals(exJson)) {
             return Future.failedFuture(new OkapiError(ErrorType.USER,
                 messages.getMessage("10203", id)));
           }
diff --git a/okapi-core/src/main/raml/okapi.raml b/okapi-core/src/main/raml/okapi.raml
index 4afa97767..089759ba5 100644
--- a/okapi-core/src/main/raml/okapi.raml
+++ b/okapi-core/src/main/raml/okapi.raml
@@ -453,7 +453,10 @@ traits:
       /_/proxy/modules.
     queryParameters:
       check:
-        description: Whether to check dependencies
+        description: Whether to check dependencies and immutability of existing modules.
+          If false, modules may be imported requiring interfaces that are not currently
+          offered by any other module. Also with a false value an existing module may be
+          updated; thus breaking immutability.
         type: boolean
         required: false
         default: true
@@ -530,7 +533,10 @@ traits:
       selected for a specific tenant.
     queryParameters:
       check:
-        description: Whether to check dependencies
+        description: Whether to check dependencies and immutability of existing modules.
+          If false, a module may be imported requiring interfaces that are not currently
+          offered by any other module. Also with a false value an existing module may
+          be updated; thus breaking immutability.
         type: boolean
         required: false
         default: true
diff --git a/okapi-core/src/test/java/org/folio/okapi/ModuleTest.java b/okapi-core/src/test/java/org/folio/okapi/ModuleTest.java
index 08969a767..6c3342219 100644
--- a/okapi-core/src/test/java/org/folio/okapi/ModuleTest.java
+++ b/okapi-core/src/test/java/org/folio/okapi/ModuleTest.java
@@ -948,6 +948,17 @@ public void testOneModule(TestContext context) {
         .body(equalTo("create: module sample-module-1+1 already exists"));
     assertEmptyReport(c);
 
+    // post it again with slight modification, but check=false, so it should be allowed, and replace the old one
+    c = api.createRestAssured3();
+    c.given()
+        .header("Content-Type", "application/json")
+        .body(docSampleModule.replace("sample.extra\"", "sample.foo\""))
+        .queryParam("check", "false")
+        .post("/_/proxy/modules")
+        .then()
+        .statusCode(201);
+    assertEmptyReport(c);
+
     given()
         .header("Content-Type", "application/json")
         .body("{}")