diff --git a/src/hb-cff-interp-common.hh b/src/hb-cff-interp-common.hh
index 824b8e28c..ad1e694d8 100644
--- a/src/hb-cff-interp-common.hh
+++ b/src/hb-cff-interp-common.hh
@@ -488,7 +488,7 @@ struct op_str_t
 
   const unsigned char *ptr = nullptr;
 
-  op_code_t  op;
+  op_code_t  op = OpCode_Invalid;
 
   uint8_t length = 0;
 };