diff --git a/inc/DifferenceEngine.php b/inc/DifferenceEngine.php
index 3c873d8d33db5c969ca85c2b43e184fbff62b29a..70877a4f2dee180a16e9a636175a0a958b6b8675 100644
--- a/inc/DifferenceEngine.php
+++ b/inc/DifferenceEngine.php
@@ -408,7 +408,7 @@ class _DiffEngine {
         $i = 0;
         $j = 0;
 
-        USE_ASSERTS && assert('count($lines) == count($changed)');
+        USE_ASSERTS && assert(count($lines) == count($changed));
         $len = count($lines);
         $other_len = count($other_changed);
 
@@ -428,7 +428,7 @@ class _DiffEngine {
                 $j++;
 
             while ($i < $len && ! $changed[$i]) {
-                USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+                USE_ASSERTS && assert($j < $other_len && ! $other_changed[$j]);
                 $i++;
                 $j++;
                 while ($j < $other_len && $other_changed[$j])
@@ -461,10 +461,10 @@ class _DiffEngine {
                     $changed[--$i] = false;
                     while ($start > 0 && $changed[$start - 1])
                         $start--;
-                    USE_ASSERTS && assert('$j > 0');
+                    USE_ASSERTS && assert($j > 0);
                     while ($other_changed[--$j])
                         continue;
-                    USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+                    USE_ASSERTS && assert($j >= 0 && !$other_changed[$j]);
                 }
 
                 /*
@@ -487,7 +487,7 @@ class _DiffEngine {
                     while ($i < $len && $changed[$i])
                         $i++;
 
-                    USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+                    USE_ASSERTS && assert($j < $other_len && ! $other_changed[$j]);
                     $j++;
                     if ($j < $other_len && $other_changed[$j]) {
                         $corresponding = $i;
@@ -504,10 +504,10 @@ class _DiffEngine {
             while ($corresponding < $i) {
                 $changed[--$start] = 1;
                 $changed[--$i] = 0;
-                USE_ASSERTS && assert('$j > 0');
+                USE_ASSERTS && assert($j > 0);
                 while ($other_changed[--$j])
                     continue;
-                USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+                USE_ASSERTS && assert($j >= 0 && !$other_changed[$j]);
             }
         }
     }