diff --git a/ext/opcache/zend_persist_calc.c b/ext/opcache/zend_persist_calc.c
index 9f26a24367b..e22b7d3952b 100644
--- a/ext/opcache/zend_persist_calc.c
+++ b/ext/opcache/zend_persist_calc.c
@@ -33,11 +33,13 @@
 
 #if ZEND_EXTENSION_API_NO > PHP_5_3_X_API_NO
 # define ADD_INTERNED_STRING(str, len) do { \
-		const char *tmp = accel_new_interned_string((str), (len), !IS_INTERNED((str)) TSRMLS_CC); \
-		if (tmp != (str)) { \
-			(str) = (char*)tmp; \
-		} else { \
-			ADD_DUP_SIZE((str), (len)); \
+		if (!IS_INTERNED(str)) { \
+			const char *tmp = accel_new_interned_string((str), (len), 1 TSRMLS_CC); \
+			if (tmp != (str)) { \
+				(str) = (char*)tmp; \
+			} else { \
+				ADD_DUP_SIZE((str), (len)); \
+			} \
 		} \
 	} while (0)
 #else