diff --git a/tools/hc-gen/src/lexer.cpp b/tools/hc-gen/src/lexer.cpp
index fd58550c767cce1d59940a4da35632378c91460a..8e2cf91e52c3f5e35657b52508ad51919cee7d08 100644
--- a/tools/hc-gen/src/lexer.cpp
+++ b/tools/hc-gen/src/lexer.cpp
@@ -256,6 +256,8 @@ bool Lexer::LexFromNumber(Token &token)
     std::string value;
     char c;
     uint64_t v = 0;
+    errno = 0;
+
     GetChar(c, false);
     switch (c) {
         case '0':