diff --git a/tests/RedisClusterTest.php b/tests/RedisClusterTest.php
index 6daa93b..0262047 100644
--- a/tests/RedisClusterTest.php
+++ b/tests/RedisClusterTest.php
@@ -284,7 +284,7 @@ class Redis_Cluster_Test extends Redis_Test {
 
         /* We should now have both prefixs' keys */
         foreach ($arr_keys as $str_prefix => $str_id) {
-            $this->assertTrue(in_array("${str_prefix}${str_id}", $arr_scan_keys));
+            $this->assertTrue(in_array("{$str_prefix}{$str_id}", $arr_scan_keys));
         }
     }
 
diff --git a/tests/RedisTest.php b/tests/RedisTest.php
index 49383d4..5d61fd6 100644
--- a/tests/RedisTest.php
+++ b/tests/RedisTest.php
@@ -5484,7 +5484,7 @@ class Redis_Test extends TestSuite
         foreach ($arr_prefixes as $str_prefix) {
             $this->redis->setOption(Redis::OPT_PREFIX, $str_prefix);
             $this->redis->set("$keyid", "LOLWUT");
-            $arr_all_keys["${str_prefix}${keyid}"] = true;
+            $arr_all_keys["{$str_prefix}{$keyid}"] = true;
         }
 
         $this->redis->setOption(Redis::OPT_SCAN, Redis::SCAN_RETRY);
@@ -5494,7 +5494,7 @@ class Redis_Test extends TestSuite
             $this->redis->setOption(Redis::OPT_PREFIX, $str_prefix);
             $it = NULL;
             $arr_keys = $this->redis->scan($it, "*$keyid*");
-            $this->assertEquals($arr_keys, ["${str_prefix}${keyid}"]);
+            $this->assertEquals($arr_keys, ["{$str_prefix}{$keyid}"]);
         }
 
         /* Unset the prefix option */