diff --git a/src/install.js b/src/install.js
index 451f062..79fd69f 100644
--- a/src/install.js
+++ b/src/install.js
@@ -9,8 +9,8 @@ export function install(_Vue) {
 
   Vue = _Vue;
 
-  const getByKey = i18nOptions => (key) => {
-    if (i18nOptions && i18nOptions.keyPrefix) {
+  const getByKey = (i18nOptions, i18nextOptions) => (key) => {
+    if (i18nOptions && i18nOptions.keyPrefix && !key.includes(i18nextOptions.nsSeparator)) {
       return `${i18nOptions.keyPrefix}.${key}`;
     }
     return key;
@@ -19,7 +19,7 @@ export function install(_Vue) {
   Vue.mixin({
     computed: {
       $t() {
-        const getKey = getByKey(this._i18nOptions);
+        const getKey = getByKey(this._i18nOptions, this.$i18n.i18next.options);
 
         if (this._i18nOptions && this._i18nOptions.namespaces) {
           const { lng, namespaces } = this._i18nOptions;
diff --git a/test/unit/render.test.js b/test/unit/render.test.js
index 6e6dc5e..f77c168 100644
--- a/test/unit/render.test.js
+++ b/test/unit/render.test.js
@@ -116,7 +116,10 @@ describe('$t loaded languages', () => {
       i18next.init({
         lng: 'en',
         resources: {
-          en: { translation: { messages: { hello: 'Hello' } } },
+          en: {
+            translation: { messages: { hello: 'Hello' }, },
+            common: { goodbye: 'Goodbye' }
+          },
         },
       });
     });
@@ -135,5 +138,20 @@ describe('$t loaded languages', () => {
       await nextTick();
       expect(text.textContent).to.equal('Hello');
     });
+
+    it('should ignore keyPrefix property if namespace prefix used', async () => {
+      const el = document.createElement('div');
+      const vm = new Vue({
+        i18n: vueI18Next,
+        i18nOptions: { keyPrefix: 'messages' },
+        render(h) {
+          return h('p', { ref: 'text' }, [this.$t('common:goodbye')]);
+        },
+      }).$mount(el);
+
+      const { text } = vm.$refs;
+      await nextTick();
+      expect(text.textContent).to.equal('Goodbye');
+    });
   });
 });