diff --git a/src/tokenize.cpp b/src/tokenize.cpp
index 470bf818a..33b87b410 100644
--- a/src/tokenize.cpp
+++ b/src/tokenize.cpp
@@ -1301,7 +1301,7 @@ void Tokenizer::simplifySizeof()
         {
             tok->deleteThis();
             std::ostringstream ostr;
-            ostr << (strlen(tok->str().c_str()) - 1);
+            ostr << Token::getStrLength(tok) + 1;
             tok->str(ostr.str());
         }
 
@@ -1311,7 +1311,7 @@ void Tokenizer::simplifySizeof()
             tok->deleteThis();
             tok->deleteNext();
             std::ostringstream ostr;
-            ostr << (strlen(tok->str().c_str()) - 1);
+            ostr << Token::getStrLength(tok) + 1;
             tok->str(ostr.str());
         }
     }
diff --git a/test/testsimplifytokens.cpp b/test/testsimplifytokens.cpp
index f43f08ad8..0a0d5f3b1 100644
--- a/test/testsimplifytokens.cpp
+++ b/test/testsimplifytokens.cpp
@@ -671,6 +671,12 @@ private:
             ASSERT_EQUALS(expected.str(), sizeof_("; sizeof \"123\""));
             ASSERT_EQUALS(expected.str(), sizeof_("; sizeof(\"123\")"));
         }
+
+        {
+            std::ostringstream expected;
+            expected << "; " << sizeof("\"quote\"");
+            ASSERT_EQUALS(expected.str(), sizeof_("; sizeof(\"\\\"quote\\\"\")"));
+        }
     }
 
     void casting()