diff --git a/dist/client-side-validations.esm.js b/dist/client-side-validations.esm.js
index bcd72be3f..2e399b96e 100644
--- a/dist/client-side-validations.esm.js
+++ b/dist/client-side-validations.esm.js
@@ -610,7 +610,8 @@ $.fn.isValid = function (validators) {
   if (obj.is('form')) {
     return validateForm(obj, validators);
   } else {
-    return validateElement(obj, validatorsFor(this[0].name, validators));
+    var form = this.closest('form');
+    return validateElement(obj, validatorsFor(this[0].name, validators, form));
   }
 };
 
@@ -624,8 +625,13 @@ var cleanNestedElementName = function cleanNestedElementName(elementName, nested
   return elementName;
 };
 
-var cleanElementName = function cleanElementName(elementName, validators) {
+var cleanElementName = function cleanElementName(elementName, validators, form) {
   elementName = elementName.replace(/\[(\w+_attributes)\]\[[\da-z_]+\](?=\[(?:\w+_attributes)\])/g, '[$1][]');
+
+  if (form.data('clientSideValidations').html_settings.type === 'SimpleForm::FormBuilder') {
+    elementName = elementName.replace(/\]\[\]$/g, ']'); // fix many association collections
+  }
+
   var nestedMatches = elementName.match(/\[(\w+_attributes)\].*\[(\w+)\]$/);
 
   if (nestedMatches) {
@@ -635,12 +641,12 @@ var cleanElementName = function cleanElementName(elementName, validators) {
   return elementName;
 };
 
-var validatorsFor = function validatorsFor(elementName, validators) {
+var validatorsFor = function validatorsFor(elementName, validators, form) {
   if (Object.prototype.hasOwnProperty.call(validators, elementName)) {
     return validators[elementName];
   }
 
-  return validators[cleanElementName(elementName, validators)] || {};
+  return validators[cleanElementName(elementName, validators, form)] || {};
 };
 
 var validateForm = function validateForm(form, validators) {
diff --git a/dist/client-side-validations.js b/dist/client-side-validations.js
index 940740a47..a75eb4c09 100644
--- a/dist/client-side-validations.js
+++ b/dist/client-side-validations.js
@@ -616,7 +616,8 @@
     if (obj.is('form')) {
       return validateForm(obj, validators);
     } else {
-      return validateElement(obj, validatorsFor(this[0].name, validators));
+      var form = this.closest('form');
+      return validateElement(obj, validatorsFor(this[0].name, validators, form));
     }
   };
 
@@ -630,8 +631,13 @@
     return elementName;
   };
 
-  var cleanElementName = function cleanElementName(elementName, validators) {
+  var cleanElementName = function cleanElementName(elementName, validators, form) {
     elementName = elementName.replace(/\[(\w+_attributes)\]\[[\da-z_]+\](?=\[(?:\w+_attributes)\])/g, '[$1][]');
+
+    if (form.data('clientSideValidations').html_settings.type === 'SimpleForm::FormBuilder') {
+      elementName = elementName.replace(/\]\[\]$/g, ']'); // fix many association collections
+    }
+
     var nestedMatches = elementName.match(/\[(\w+_attributes)\].*\[(\w+)\]$/);
 
     if (nestedMatches) {
@@ -641,12 +647,12 @@
     return elementName;
   };
 
-  var validatorsFor = function validatorsFor(elementName, validators) {
+  var validatorsFor = function validatorsFor(elementName, validators, form) {
     if (Object.prototype.hasOwnProperty.call(validators, elementName)) {
       return validators[elementName];
     }
 
-    return validators[cleanElementName(elementName, validators)] || {};
+    return validators[cleanElementName(elementName, validators, form)] || {};
   };
 
   var validateForm = function validateForm(form, validators) {
diff --git a/src/main.js b/src/main.js
index 91f2553cc..c43ac13e7 100644
--- a/src/main.js
+++ b/src/main.js
@@ -66,7 +66,8 @@ $.fn.isValid = function (validators) {
   if (obj.is('form')) {
     return validateForm(obj, validators)
   } else {
-    return validateElement(obj, validatorsFor(this[0].name, validators))
+    const form = this.closest('form')
+    return validateElement(obj, validatorsFor(this[0].name, validators, form))
   }
 }
 
@@ -80,9 +81,13 @@ const cleanNestedElementName = (elementName, nestedMatches, validators) => {
   return elementName
 }
 
-const cleanElementName = (elementName, validators) => {
+const cleanElementName = (elementName, validators, form) => {
   elementName = elementName.replace(/\[(\w+_attributes)\]\[[\da-z_]+\](?=\[(?:\w+_attributes)\])/g, '[$1][]')
 
+  if (form.data('clientSideValidations').html_settings.type === 'SimpleForm::FormBuilder') {
+    elementName = elementName.replace(/\]\[\]$/g, ']') // fix many association collections
+  }
+
   const nestedMatches = elementName.match(/\[(\w+_attributes)\].*\[(\w+)\]$/)
 
   if (nestedMatches) {
@@ -92,12 +97,12 @@ const cleanElementName = (elementName, validators) => {
   return elementName
 }
 
-const validatorsFor = (elementName, validators) => {
+const validatorsFor = (elementName, validators, form) => {
   if (Object.prototype.hasOwnProperty.call(validators, elementName)) {
     return validators[elementName]
   }
 
-  return validators[cleanElementName(elementName, validators)] || {}
+  return validators[cleanElementName(elementName, validators, form)] || {}
 }
 
 const validateForm = (form, validators) => {
diff --git a/vendor/assets/javascripts/rails.validations.js b/vendor/assets/javascripts/rails.validations.js
index 940740a47..a75eb4c09 100644
--- a/vendor/assets/javascripts/rails.validations.js
+++ b/vendor/assets/javascripts/rails.validations.js
@@ -616,7 +616,8 @@
     if (obj.is('form')) {
       return validateForm(obj, validators);
     } else {
-      return validateElement(obj, validatorsFor(this[0].name, validators));
+      var form = this.closest('form');
+      return validateElement(obj, validatorsFor(this[0].name, validators, form));
     }
   };
 
@@ -630,8 +631,13 @@
     return elementName;
   };
 
-  var cleanElementName = function cleanElementName(elementName, validators) {
+  var cleanElementName = function cleanElementName(elementName, validators, form) {
     elementName = elementName.replace(/\[(\w+_attributes)\]\[[\da-z_]+\](?=\[(?:\w+_attributes)\])/g, '[$1][]');
+
+    if (form.data('clientSideValidations').html_settings.type === 'SimpleForm::FormBuilder') {
+      elementName = elementName.replace(/\]\[\]$/g, ']'); // fix many association collections
+    }
+
     var nestedMatches = elementName.match(/\[(\w+_attributes)\].*\[(\w+)\]$/);
 
     if (nestedMatches) {
@@ -641,12 +647,12 @@
     return elementName;
   };
 
-  var validatorsFor = function validatorsFor(elementName, validators) {
+  var validatorsFor = function validatorsFor(elementName, validators, form) {
     if (Object.prototype.hasOwnProperty.call(validators, elementName)) {
       return validators[elementName];
     }
 
-    return validators[cleanElementName(elementName, validators)] || {};
+    return validators[cleanElementName(elementName, validators, form)] || {};
   };
 
   var validateForm = function validateForm(form, validators) {