diff --git a/src/Compiler.php b/src/Compiler.php
index af20970e..02ac275c 100644
--- a/src/Compiler.php
+++ b/src/Compiler.php
@@ -855,7 +855,6 @@ protected function compileMedia(Block $media)
 
                     $this->scope->children[] = $annotation;
                 }
-
             }
 
             $this->compileChildrenNoReturn($media->children, $this->scope);
@@ -2630,6 +2629,9 @@ protected function reduce($value, $inExp = false)
 
             case Type::T_INTERPOLATE:
                 $value[1] = $this->reduce($value[1]);
+                if ($inExp) {
+                    return $value[1];
+                }
 
                 return $value;
 
@@ -3372,7 +3374,7 @@ protected function multiplySelectors(Environment $env, $selfParent = null)
                                 $selectors[serialize($s)] = $s;
                             }
                         } else {
-                            $s = $this->joinSelectors($parent, $selector,$stillHasSelf);
+                            $s = $this->joinSelectors($parent, $selector, $stillHasSelf);
                             $selectors[serialize($s)] = $s;
                         }
                     }
diff --git a/tests/inputs/interpolation.scss b/tests/inputs/interpolation.scss
index 0819a7c6..45a5133b 100644
--- a/tests/inputs/interpolation.scss
+++ b/tests/inputs/interpolation.scss
@@ -132,4 +132,11 @@ div {
 
 .pagination {
   @include pagination-mixin(5px);
+}
+
+@mixin set-border($width) {
+    border: $width solid #000;
+}
+.element {
+    @include set-border(#{2px}); // compiles to "2px solid #000"
 }
\ No newline at end of file
diff --git a/tests/outputs/interpolation.css b/tests/outputs/interpolation.css
index be302600..d9fd10e5 100644
--- a/tests/outputs/interpolation.css
+++ b/tests/outputs/interpolation.css
@@ -74,3 +74,6 @@ a.badge {
 
 .pagination .page-item:first-child .page-link {
   border-radius: 5px; }
+
+.element {
+  border: 2px solid #000; }
diff --git a/tests/outputs_numbered/interpolation.css b/tests/outputs_numbered/interpolation.css
index 768df93a..da509491 100644
--- a/tests/outputs_numbered/interpolation.css
+++ b/tests/outputs_numbered/interpolation.css
@@ -93,3 +93,6 @@ a.badge {
 /* line 126, inputs/interpolation.scss */
   .pagination .page-item:first-child .page-link {
     border-radius: 5px; }
+/* line 140, inputs/interpolation.scss */
+.element {
+  border: 2px solid #000; }