diff --git a/app.yaml b/app.yaml
index 85293e6..6f5eab8 100644
--- a/app.yaml
+++ b/app.yaml
@@ -1,6 +1,6 @@
 #application: bash-minifier
 #version: 1
-runtime: python27
+runtime: python3
 api_version: 1
 threadsafe: true
 
diff --git a/minifier.py b/minifier.py
old mode 100755
new mode 100644
index a430d7c..d1fb2d0
--- a/minifier.py
+++ b/minifier.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 
 import sys
 
@@ -19,7 +19,7 @@ def is_group_opening(self):
         def __eq__(self, other):
             if isinstance(other, BashFileIterator._Delimiter):
                 return other.character == self.character
-            elif isinstance(other, basestring):
+            elif isinstance(other, str):
                 return other == self.character
             return False
 
@@ -213,7 +213,6 @@ def close_heredoc():
             self.pos += 1
 
         assert not self.isInsideGroup(), 'Invalid syntax'
-        raise StopIteration
 
     def isEscaped(self):
         return self.pos in self._indices_of_escaped_characters
diff --git a/run_tests.sh b/run_tests.sh
index 7a08616..eec0a29 100755
--- a/run_tests.sh
+++ b/run_tests.sh
@@ -5,7 +5,7 @@ passed=0
 failed=0
 for f in t*.sh; do
     echo -n "$f "
-    python ../minifier.py $f > _tmp_$f
+    python3 ../minifier.py $f > _tmp_$f
     if [ `diff _tmp_$f minified_$f | wc -c` -ne 0 ]; then
         failed=$((failed+1))
         echo FAILED
@@ -16,4 +16,4 @@ for f in t*.sh; do
     rm _tmp_$f
 done
 echo PASSED $passed, FAILED $failed
-popd > /dev/null
\ No newline at end of file
+popd > /dev/null