diff --git a/stylesheets/_SassyLists.scss b/stylesheets/_SassyLists.scss
index 96569bf..f134d87 100644
--- a/stylesheets/_SassyLists.scss
+++ b/stylesheets/_SassyLists.scss
@@ -4,6 +4,7 @@
 // Repository: https://github.com/at-import/functions/
 
 @import 'helpers/missing-dependencies';
+@import 'helpers/safe-call-function';
 @import 'helpers/str-compare';
 @import 'helpers/true';
 @import 'helpers/is-number';
diff --git a/stylesheets/functions/_every.scss b/stylesheets/functions/_every.scss
index 799cdc8..852d2b6 100644
--- a/stylesheets/functions/_every.scss
+++ b/stylesheets/functions/_every.scss
@@ -3,9 +3,9 @@
 ///
 /// @ignore Documentation: http://at-import.github.io/SassyLists/documentation/#function-sl-every
 ///
-/// @param {List}    $list     - list to run test against
-/// @param {String}  $function - function to run against every item from list
-/// @param {ArgList} $args     - extra arguments to pass to the function
+/// @param {List}             $list     - list to run test against
+/// @param {Function|String}  $function - function or function name string to run against every item from list
+/// @param {ArgList}          $args     - extra arguments to pass to the function
 ///
 /// @example
 /// sl-every(1 2 3, unitless)
@@ -20,10 +20,10 @@
 
 @function sl-every($list, $function, $args...) {
   @each $item in $list {
-    @if not call($function, $item, $args...) {
+    @if not sl-safe-call-function($function, $item, $args...) {
       @return false;
-    } 
+    }
   }
-  
+
   @return true;
 }
diff --git a/stylesheets/functions/_some.scss b/stylesheets/functions/_some.scss
index d6945b8..43eed23 100644
--- a/stylesheets/functions/_some.scss
+++ b/stylesheets/functions/_some.scss
@@ -3,9 +3,9 @@
 ///
 /// @ignore Documentation: http://at-import.github.io/SassyLists/documentation/#function-sl-some
 ///
-/// @param {List}    $list     - list to run test against
-/// @param {String}  $function - function to run against every item from list
-/// @param {ArgList} $args     - extra arguments to pass to the function
+/// @param {List}             $list     - list to run test against
+/// @param {Function|String}  $function - function or function name string to run against every item from list
+/// @param {ArgList}          $args     - extra arguments to pass to the function
 ///
 /// @example
 /// sl-some(1 2 3, unitless)
@@ -21,13 +21,13 @@
 ///
 /// @return {Bool}
 ///
- 
+
 @function sl-some($list, $function, $args...) {
   @each $item in $list {
-    @if call($function, $item, $args...) {
+    @if sl-safe-call-function($function, $item, $args...) {
       @return true;
-    } 
+    }
   }
-  
+
   @return false;
 }
diff --git a/stylesheets/functions/_walk.scss b/stylesheets/functions/_walk.scss
index 23f9f17..3b78602 100644
--- a/stylesheets/functions/_walk.scss
+++ b/stylesheets/functions/_walk.scss
@@ -3,9 +3,9 @@
 ///
 /// @ignore Documentation: http://at-import.github.io/SassyLists/documentation/#function-sl-walk
 ///
-/// @param {List}    $list     - list to update
-/// @param {String}  $function - function to call on each value
-/// @param {ArgList} $args     - optional function arguments
+/// @param {List}             $list     - list to update
+/// @param {Function|String}  $function - function or function name string to call on each value
+/// @param {ArgList}          $args     - optional function arguments
 ///
 /// @throws There is no `$function` function for `sl-walk`.
 ///
@@ -18,18 +18,18 @@
 ///
 /// @return {List | Null}
 ///
- 
+
 @function sl-walk($list, $function, $args...) {
   $_: sl-missing-dependencies('sl-to-map', 'sl-to-list');
-  
+
   @if not function-exists($function) {
     @error 'There is no `#{$function}` function for `sl-walk`.';
   }
 
   @each $index, $value in sl-to-map($list) {
     $arguments: join($value, $args);
-    $list: set-nth($list, $index, call($function, $arguments...));
+    $list: set-nth($list, $index, sl-safe-call-function($function, $arguments...));
   }
-  
+
   @return sl-to-list($list);
 }
diff --git a/stylesheets/helpers/_safe-call-function.scss b/stylesheets/helpers/_safe-call-function.scss
new file mode 100644
index 0000000..e3256d8
--- /dev/null
+++ b/stylesheets/helpers/_safe-call-function.scss
@@ -0,0 +1,28 @@
+///
+/// Polyfill for the `call` function supporting both functions and strings.
+///
+/// In order to improve modular namespacing, LibSass 4 only accepts first-class
+/// functions as argument so functions are called in their own context.
+/// In most case, `get-function()` must only be used by the user in its own
+/// context. It is used in this library to keep a maximum compatibility.
+/// End developer must be encouraged to use first-class functions.
+///
+/// @link http://oddbird.net/2017/03/30/safe-get
+/// @link http://sass.logdown.com/posts/809572-sass-35-release-candidate
+///
+/// @access private
+///
+/// @param {Function|String} $func - Function or name of the function to call
+/// @param {*} $args... - Arguments to call the function with
+///
+/// @return {*}
+///
+@function sl-safe-call-function($func, $args...) {
+  @if (function-exists('get-function') and type-of($func) == 'string') {
+    @warn '#{$func} function name was passed for call(). It is recommended to use `get-function()` and first-class functions instead. See http://oddbird.net/2017/03/30/safe-get';
+    @return call(get-function($func),  $args...);
+  }
+  @else {
+    @return call($func, $args...);
+  }
+}