diff --git a/src/regcomp.c b/src/regcomp.c
index 69d4b95..380f441 100644
--- a/src/regcomp.c
+++ b/src/regcomp.c
@@ -3880,7 +3880,7 @@ reduce_string_list(Node* node)
     {
       Node* prev;
       Node* curr;
-      Node* prev_node;
+      Node* prev_node = NULL;
       Node* next_node;
 
       prev = NULL_NODE;
diff --git a/src/regexec.c b/src/regexec.c
index ce498c6..6848c0f 100644
--- a/src/regexec.c
+++ b/src/regexec.c
@@ -4216,7 +4216,7 @@ regset_search_body_position_lead(OnigRegSet* set,
 {
   int r, n, i;
   UChar *s, *prev;
-  UChar *low, *high, *low_prev;
+  UChar *low, *high, *low_prev = NULL;
   UChar* sch_range;
   regex_t* reg;
   OnigEncoding enc;