diff --git a/package.json b/package.json
index 7c2d00a..1ca6043 100644
--- a/package.json
+++ b/package.json
@@ -32,7 +32,7 @@
     "Respond.js": "github:scottjehl/Respond#1.4.2",
     "anchor-js": "^3.2.1",
     "autoprefixer": "^6.4.0",
-    "bootstrap": "^3.3.7",
+    "bootstrap": "^4.0.0-alpha.6",
     "bootstrap-sass": "^3.3.7",
     "diff": "^2.2.3",
     "grunt": "^1.0.1",
diff --git a/src/build.scss b/src/build.scss
index 68c0007..1a80d48 100755
--- a/src/build.scss
+++ b/src/build.scss
@@ -1,3 +1,6 @@
-@import "../node_modules/bootstrap-sass/assets/stylesheets/bootstrap/variables";
-@import "../node_modules/bootstrap-sass/assets/stylesheets/bootstrap/mixins";
+@import "../node_modules/bootstrap/scss/variables";
+@import "../node_modules/bootstrap/scss/mixins";
+$caret-width:            .3rem;
+@import "select2-bootstrap4.vars";
 @import "select2-bootstrap.scss";
+@import "select2-bootstrap4.after";
diff --git a/src/select2-bootstrap.scss b/src/select2-bootstrap.scss
index 1afafdc..029994a 100755
--- a/src/select2-bootstrap.scss
+++ b/src/select2-bootstrap.scss
@@ -541,7 +541,7 @@ $s2bs-form-control-transition: border-color ease-in-out .15s, box-shadow ease-in
    */
 
   /* 1 */
-  .select2-selection--single.input-sm,
+  .select2-selection--single.form-control-sm,
   .input-group-sm & .select2-selection--single,
   .form-group-sm & .select2-selection--single {
     border-radius: $s2bs-border-radius-small;
@@ -556,7 +556,7 @@ $s2bs-form-control-transition: border-color ease-in-out .15s, box-shadow ease-in
     }
   }
 
-  .select2-selection--multiple.input-sm,
+  .select2-selection--multiple.form-control-sm,
   .input-group-sm & .select2-selection--multiple,
   .form-group-sm & .select2-selection--multiple {
     min-height: $s2bs-input-height-small;
@@ -581,7 +581,7 @@ $s2bs-form-control-transition: border-color ease-in-out .15s, box-shadow ease-in
     }
   }
 
-  .select2-selection--single.input-lg,
+  .select2-selection--single.form-control-lg,
   .input-group-lg & .select2-selection--single,
   .form-group-lg & .select2-selection--single {
     border-radius: $s2bs-border-radius-large;
@@ -603,7 +603,7 @@ $s2bs-form-control-transition: border-color ease-in-out .15s, box-shadow ease-in
     }
   }
 
-  .select2-selection--multiple.input-lg,
+  .select2-selection--multiple.form-control-lg,
   .input-group-lg & .select2-selection--multiple,
   .form-group-lg & .select2-selection--multiple {
     min-height: $s2bs-input-height-large;
@@ -629,7 +629,7 @@ $s2bs-form-control-transition: border-color ease-in-out .15s, box-shadow ease-in
     }
   }
 
-  .select2-selection.input-lg.select2-container--open {
+  .select2-selection.form-control-lg.select2-container--open {
     @include dropdown-arrow;
   }
 
diff --git a/src/select2-bootstrap4.after.scss b/src/select2-bootstrap4.after.scss
new file mode 100644
index 0000000..85861bb
--- /dev/null
+++ b/src/select2-bootstrap4.after.scss
@@ -0,0 +1,36 @@
+// Import this file after select2 bootstrap theme. Content won't be centered if you don't include this file.
+.select2-container--bootstrap {
+	.select2-selection--multiple {
+		.select2-selection__choice {
+			margin-top: calc(#{$s2bs-padding-base-vertical} - 1px);
+		}
+
+		.select2-search--inline .select2-search__field {
+			height: $s2bs-input-height-base;
+		}
+	}
+
+	.select2-selection--multiple.form-control-sm,
+	.input-group-sm & .select2-selection--multiple,
+	.form-group-sm & .select2-selection--multiple {
+		.select2-selection__choice {
+			margin-top: calc(#{$s2bs-padding-small-vertical} - 1px);
+		}
+
+		.select2-search--inline .select2-search__field {
+			height: $s2bs-input-height-small;
+		}
+	}
+
+	.select2-selection--multiple.form-control-lg,
+	.input-group-lg & .select2-selection--multiple,
+	.form-group-lg & .select2-selection--multiple {
+		.select2-selection__choice {
+			margin-top: calc(#{$s2bs-padding-large-vertical} - 1px) ;
+		}
+
+		.select2-search--inline .select2-search__field {
+			height: $s2bs-input-height-large;
+		}
+	}
+}
\ No newline at end of file
diff --git a/src/select2-bootstrap4.vars.scss b/src/select2-bootstrap4.vars.scss
new file mode 100644
index 0000000..0555f29
--- /dev/null
+++ b/src/select2-bootstrap4.vars.scss
@@ -0,0 +1,34 @@
+// Overrides of Select2 SASS variables to make it work with Bootstrap 4 and match its look.
+// Import this BEFORE https://github.com/select2/select2-bootstrap-theme SASS files or SASS compilation will fail
+// Since there is no official Bootstrap 4 theme for Select 2 this is a good fallback.
+
+$screen-sm-min: 576px !default;
+$btn-default-color: $btn-secondary-color !default;
+
+$s2bs-input-border: $input-border-color !default;
+$s2bs-clear-selection-hover-color: $btn-secondary-color !default;
+$s2bs-remove-choice-hover-color: $btn-secondary-color !default;
+$s2bs-border-radius-base: $border-radius !default;
+$s2bs-border-radius-large: $border-radius-lg !default;
+$s2bs-border-radius-small: $border-radius-sm !default;
+$s2bs-btn-default-bg: $btn-secondary-bg !default;
+$s2bs-btn-default-border: $btn-secondary-border !default;
+$s2bs-caret-width-base: .25rem !default; // 4px
+$s2bs-caret-width-large: .3125rem !default; // 5px
+$s2bs-font-size-base: $font-size-base !default;
+$s2bs-font-size-large: $font-size-lg !default;
+$s2bs-font-size-small: $font-size-sm !default;
+$s2bs-padding-base-horizontal: $input-padding-x !default;
+$s2bs-padding-large-horizontal: $input-padding-x-lg !default;
+$s2bs-padding-small-horizontal: $input-padding-x-sm !default;
+$s2bs-padding-base-vertical: $input-padding-y  !default;
+$s2bs-padding-large-vertical: $input-padding-y-lg !default;
+$s2bs-padding-small-vertical: $input-padding-y-sm !default;
+$s2bs-line-height-base: $input-line-height !default;
+$s2bs-line-height-large: $input-line-height !default;
+$s2bs-line-height-small: $input-line-height !default;
+$s2bs-input-height-base: calc(#{$input-padding-y * 2 + $input-line-height} + #{$border-width * 2}) !default;
+$s2bs-input-height-large: calc(#{$input-padding-y-lg * 2 + $input-line-height} + #{$border-width * 2}) !default;
+$s2bs-input-height-small: calc(#{$input-padding-y-sm * 2 + $input-line-height} + #{$border-width * 2}) !default;
+
+$s2bs-selection-choice-border-radius: $border-radius !default;
\ No newline at end of file