diff --git a/src/Psalm/CodeLocation.php b/src/Psalm/CodeLocation.php
index 588a83230e5..15ed58cea67 100644
--- a/src/Psalm/CodeLocation.php
+++ b/src/Psalm/CodeLocation.php
@@ -11,11 +11,11 @@
 use function preg_replace;
 use Psalm\Internal\Analyzer\CommentAnalyzer;
 use function str_replace;
-use function strlen;
-use function strpos;
-use function strrpos;
-use function substr;
-use function substr_count;
+use function mb_strlen;
+use function mb_strpos;
+use function mb_strrpos;
+use function mb_substr;
+use function mb_substr_count;
 use function trim;
 
 class CodeLocation
@@ -156,12 +156,12 @@ private function calculateRealLocation(): void
 
         $file_contents = $codebase->getFileContents($this->file_path);
 
-        $file_length = strlen($file_contents);
+        $file_length = mb_strlen($file_contents);
 
         $search_limit = $this->single_line ? $this->selection_start : $this->selection_end;
 
         if ($search_limit <= $file_length) {
-            $preview_end = strpos(
+            $preview_end = mb_strpos(
                 $file_contents,
                 "\n",
                 $search_limit
@@ -183,7 +183,7 @@ private function calculateRealLocation(): void
         ) {
             $preview_lines = explode(
                 "\n",
-                substr(
+                mb_substr(
                     $file_contents,
                     $this->preview_start,
                     $this->selection_start - $this->preview_start - 1
@@ -195,7 +195,7 @@ private function calculateRealLocation(): void
             $comment_line_offset = $this->docblock_line_number - $this->docblock_start_line_number;
 
             for ($i = 0; $i < $comment_line_offset; ++$i) {
-                $preview_offset += strlen($preview_lines[$i]) + 1;
+                $preview_offset += mb_strlen($preview_lines[$i]) + 1;
             }
 
             if (!isset($preview_lines[$i])) {
@@ -206,10 +206,10 @@ private function calculateRealLocation(): void
 
             $indentation = (int)strpos($key_line, '@');
 
-            $key_line = trim(preg_replace('@\**/\s*@', '', substr($key_line, $indentation)));
+            $key_line = trim(preg_replace('@\**/\s*@', '', mb_substr($key_line, $indentation)));
 
             $this->selection_start = $preview_offset + $indentation + $this->preview_start;
-            $this->selection_end = $this->selection_start + strlen($key_line);
+            $this->selection_end = $this->selection_start + mb_strlen($key_line);
         }
 
         if ($this->regex_type !== null) {
@@ -258,7 +258,7 @@ private function calculateRealLocation(): void
                     throw new \UnexpectedValueException('Unrecognised regex type ' . $this->regex_type);
             }
 
-            $preview_snippet = substr(
+            $preview_snippet = mb_substr(
                 $file_contents,
                 $this->selection_start,
                 $this->selection_end - $this->selection_start
@@ -271,7 +271,7 @@ private function calculateRealLocation(): void
 
             if (preg_match($regex, $preview_snippet, $matches, PREG_OFFSET_CAPTURE)) {
                 $this->selection_start = $this->selection_start + (int)$matches[$match_offset][1];
-                $this->selection_end = $this->selection_start + strlen((string)$matches[$match_offset][0]);
+                $this->selection_end = $this->selection_start + mb_strlen((string)$matches[$match_offset][0]);
             }
         }
 
@@ -279,7 +279,7 @@ private function calculateRealLocation(): void
         $this->preview_start = (int)strrpos(
             $file_contents,
             "\n",
-            min($this->preview_start, $this->selection_start) - strlen($file_contents)
+            min($this->preview_start, $this->selection_start) - mb_strlen($file_contents)
         ) + 1;
 
         $this->selection_start = max($this->preview_start, $this->selection_start);
@@ -289,7 +289,7 @@ private function calculateRealLocation(): void
             $this->preview_end = (int)strrpos(
                 $file_contents,
                 "\n",
-                $this->selection_end + 200 - strlen($file_contents)
+                $this->selection_end + 200 - mb_strlen($file_contents)
             );
 
             // if the line is over 200 characters long
@@ -298,20 +298,20 @@ private function calculateRealLocation(): void
             }
         }
 
-        $this->snippet = substr($file_contents, $this->preview_start, $this->preview_end - $this->preview_start);
-        $this->text = substr($file_contents, $this->selection_start, $this->selection_end - $this->selection_start);
+        $this->snippet = mb_substr($file_contents, $this->preview_start, $this->preview_end - $this->preview_start);
+        $this->text = mb_substr($file_contents, $this->selection_start, $this->selection_end - $this->selection_start);
 
         // reset preview start to beginning of line
         $this->column_from = $this->selection_start -
-            (int)strrpos($file_contents, "\n", $this->selection_start - strlen($file_contents));
+            (int)strrpos($file_contents, "\n", $this->selection_start - mb_strlen($file_contents));
 
-        $newlines = substr_count($this->text, "\n");
+        $newlines = mb_substr_count($this->text, "\n");
 
         if ($newlines) {
-            $last_newline_pos = strrpos($file_contents, "\n", $this->selection_end - strlen($file_contents) - 1);
+            $last_newline_pos = mb_strrpos($file_contents, "\n", $this->selection_end - mb_strlen($file_contents) - 1);
             $this->column_to = $this->selection_end - (int)$last_newline_pos;
         } else {
-            $this->column_to = $this->column_from + strlen($this->text);
+            $this->column_to = $this->column_from + mb_strlen($this->text);
         }
 
         $this->end_line_number = $this->getLineNumber() + $newlines;