diff --git a/src/error_handling.c b/src/error_handling.c
index a0605373..ce99e66b 100644
--- a/src/error_handling.c
+++ b/src/error_handling.c
@@ -25,6 +25,7 @@ extern "C"
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#define __STDC_WANT_LIB_EXT1__ 1
 #include <string.h>
 
 #include <rcutils/allocator.h>
@@ -198,7 +199,11 @@ rcutils_set_error_state(
   error_state.line_number = line_number;
 #if RCUTILS_REPORT_ERROR_HANDLING_ERRORS
   // Only warn of overwritting if the new error is different from the old ones.
+#ifdef __STDC_LIB_EXT1__
+  size_t characters_to_compare = strnlen_s(error_string, RCUTILS_ERROR_MESSAGE_MAX_LENGTH);
+#else
   size_t characters_to_compare = strnlen(error_string, RCUTILS_ERROR_MESSAGE_MAX_LENGTH);
+#endif
   // assumption is that message length is <= max error string length
   static_assert(
     sizeof(gtls_rcutils_error_state.message) <= sizeof(gtls_rcutils_error_string.str),
diff --git a/src/error_handling_helpers.h b/src/error_handling_helpers.h
index 4914c4fe..07ef144a 100644
--- a/src/error_handling_helpers.h
+++ b/src/error_handling_helpers.h
@@ -36,6 +36,7 @@
 #endif
 #include <assert.h>
 #include <stdlib.h>
+#define __STDC_WANT_LIB_EXT1__ 1
 #include <string.h>
 
 #include <rcutils/error_handling.h>
@@ -130,7 +131,11 @@ __rcutils_convert_uint64_t_into_c_str(uint64_t number, char * buffer, size_t buf
   buffer[i] = '\0';
 
   // reverse the string in place
+#ifdef __STDC_LIB_EXT1__
+  __rcutils_reverse_str(buffer, strnlen_s(buffer, 21));
+#else
   __rcutils_reverse_str(buffer, strnlen(buffer, 21));
+#endif
 }
 
 // do not use externally, internal function which is only to be used by error_handling.c