diff --git a/src/gmio_core/config.h.cmake b/src/gmio_core/config.h.cmake
index 09cb3fe..e84fb4d 100644
--- a/src/gmio_core/config.h.cmake
+++ b/src/gmio_core/config.h.cmake
@@ -58,4 +58,9 @@
 #  define GMIO_TARGET_ARCH_BIT_SIZE  @GMIO_TARGET_ARCH_BIT_SIZE@
 #endif
 
+/* gmio_core/internal/string_parse.h */
+#ifndef GMIO_USE_FAST_ATOF
+#  define GMIO_USE_FAST_ATOF
+#endif
+
 #endif /* GMIO_CONFIG_H_CMAKE */
diff --git a/src/gmio_core/internal/string_parse.h b/src/gmio_core/internal/string_parse.h
index 9b401ec..27d80f5 100644
--- a/src/gmio_core/internal/string_parse.h
+++ b/src/gmio_core/internal/string_parse.h
@@ -22,7 +22,6 @@
 /* For implementation section */
 #include "helper_stream.h"
 #include "string_utils.h"
-#define GMIO_USE_FAST_ATOF
 #ifdef GMIO_USE_FAST_ATOF
 #  include "fast_atof.h"
 #endif