diff --git a/nac3core/irrt/irrt/string.hpp b/nac3core/irrt/irrt/string.hpp
index d873b9f3..036b56a7 100644
--- a/nac3core/irrt/irrt/string.hpp
+++ b/nac3core/irrt/irrt/string.hpp
@@ -4,7 +4,7 @@
 
 namespace {
 template<typename SizeT>
-int32_t __nac3_str_eq_impl(const char* str1, SizeT len1, const char* str2, SizeT len2) {
+SizeT __nac3_str_eq_impl(const char* str1, SizeT len1, const char* str2, SizeT len2) {
     if (len1 != len2){
         return 0;
     }
@@ -13,7 +13,7 @@ int32_t __nac3_str_eq_impl(const char* str1, SizeT len1, const char* str2, SizeT
 }  // namespace
 
 extern "C" {
-int32_t nac3_str_eq(const char* str1, uint64_t len1, const char* str2, uint64_t len2) {
+int64_t nac3_str_eq(const char* str1, uint64_t len1, const char* str2, uint64_t len2) {
     return __nac3_str_eq_impl<uint64_t>(str1, len1, str2, len2);
 }