diff --git a/pywikidiff2/pywikidiff2.cpp b/pywikidiff2/pywikidiff2.cpp
index d2286bd..bf705b1 100644
--- a/pywikidiff2/pywikidiff2.cpp
+++ b/pywikidiff2/pywikidiff2.cpp
@@ -104,13 +104,16 @@ static Wikidiff2::String char_to_string(char* cstr){
 }
 
 static Wikidiff2::String wikidiff2_inline_json_diff(pywikidiff2Obj *self, char* text1, char* text2){
+  Wikidiff2::String ret;
+  Py_BEGIN_ALLOW_THREADS
   Wikidiff2::String str1(text1, strlen(text1));
   Wikidiff2::String str2(text2, strlen(text2));
   Wikidiff2 wikidiff2( *(&self->config));
   InlineJSONFormatter formatter;
   wikidiff2.addFormatter(formatter);
   wikidiff2.execute(str1, str2);
-  Wikidiff2::String ret = formatter.getResult().str();
+  ret = formatter.getResult().str();
+  Py_END_ALLOW_THREADS
   return ret;
 }