diff --git a/src/FlexLexer.h b/src/FlexLexer.h
index bad4ce0..6f46c49 100644
--- a/src/FlexLexer.h
+++ b/src/FlexLexer.h
@@ -173,8 +173,8 @@ class yyFlexLexer : public FlexLexer {
 	int yy_did_buffer_switch_on_eof;
 
 
-	size_t yy_buffer_stack_top; /**< index of top of stack. */
-	size_t yy_buffer_stack_max; /**< capacity of stack. */
+    std::size_t yy_buffer_stack_top; /**< index of top of stack. */
+    std::size_t yy_buffer_stack_max; /**< capacity of stack. */
 	struct yy_buffer_state ** yy_buffer_stack; /**< Stack as an array. */
 	void yyensure_buffer_stack(void);
 
diff --git a/src/json_scanner.cc b/src/json_scanner.cc
index 58f7d00..441888e 100644
--- a/src/json_scanner.cc
+++ b/src/json_scanner.cc
@@ -168,7 +168,7 @@ typedef struct yy_buffer_state *YY_BUFFER_STATE;
 
 #ifndef YY_TYPEDEF_YY_SIZE_T
 #define YY_TYPEDEF_YY_SIZE_T
-typedef size_t yy_size_t;
+typedef std::size_t yy_size_t;
 #endif
 
 extern yy_size_t yyleng;