diff --git a/app/assets/stylesheets/application.scss b/app/assets/stylesheets/application.scss
index 335b76c..1787f5c 100644
--- a/app/assets/stylesheets/application.scss
+++ b/app/assets/stylesheets/application.scss
@@ -2,7 +2,7 @@
 @import "bootstrap-markdown/css/bootstrap-markdown.min";
 @import "font-awesome";
 @import "select2/dist/css/select2";
-@import "select2-bootstrap-theme/dist/select2-bootstrap.min";
+@import "select2-theme-bootstrap4/dist/select2-bootstrap";
 @import "dragula-with-animation/dist/dragula";
 
 $footer-height: 60px;
@@ -111,3 +111,32 @@ textarea.post-content {
 .d-none, .d-block {
   transition: all 3s;
 }
+
+/* Select2 Bootstrap4 Validation */
+
+.was-validated {
+  .form-control {
+    &:invalid {
+      ~ .select2-container--bootstrap {
+        border: 1px solid #dc3545;
+        border-radius: 0.25rem;
+
+        .select2-dropdown {
+          border: 1px solid #dc3545;
+          border-radius: 0.25rem;
+        }
+      }
+    }
+    &:valid {
+      ~ .select2-container--bootstrap {
+        border: 1px solid #28a745;
+        border-radius: 0.25rem;
+
+        .select2-dropdown {
+          border: 1px solid #28a745;
+          border-radius: 0.25rem;
+        }
+      }
+    }
+  }
+}
diff --git a/package.json b/package.json
index 6de28d7..fb02118 100644
--- a/package.json
+++ b/package.json
@@ -11,6 +11,7 @@
     "popper.js": "^1.12.9",
     "select2": "4.0.5",
     "select2-bootstrap-theme": "https://github.com/angel-vladov/select2-bootstrap-theme",
+    "select2-theme-bootstrap4": "^0.2.0-beta.2",
     "table-dragger": "^1.0.2"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 93ef77d..694bf3f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -137,6 +137,10 @@ rx@^4.1.0:
   version "0.1.0-beta.10"
   resolved "https://github.com/angel-vladov/select2-bootstrap-theme#4fb604838e79150161fc636dbeb3b3022c034cda"
 
+select2-theme-bootstrap4@^0.2.0-beta.2:
+  version "0.2.0-beta.2"
+  resolved "https://registry.yarnpkg.com/select2-theme-bootstrap4/-/select2-theme-bootstrap4-0.2.0-beta.2.tgz#4295be07585939d6094b37ce65168d77be99c24b"
+
 select2@4.0.5:
   version "4.0.5"
   resolved "https://registry.yarnpkg.com/select2/-/select2-4.0.5.tgz#7aac50692561985b34d3b82ec55e226f8960d40a"