diff --git a/include/nuttx/compiler.h b/include/nuttx/compiler.h
index 49f9fdbeca8..d6ea6c9dec2 100644
--- a/include/nuttx/compiler.h
+++ b/include/nuttx/compiler.h
@@ -260,7 +260,7 @@
 
 /* GCC supports inlined functions for version C99 and above */
 
-#  if defined(__cplusplus) || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L)
+#  if defined(__cplusplus) || !defined(__STDC_VERSION__) || __STDC_VERSION__ >= 199901L
 #    define CONFIG_HAVE_INLINE 1
 #  else
 #    undef CONFIG_HAVE_INLINE