diff --git a/include/ruby/missing.h b/include/ruby/missing.h
index 3474ca256f..7dbd29ffd1 100644
--- a/include/ruby/missing.h
+++ b/include/ruby/missing.h
@@ -162,6 +162,8 @@ RUBY_EXTERN const union bytesequence4_or_float rb_nan;
 #    include <ieeefp.h>
 #    endif
 #  define isinf(x) (!finite(x) && !isnan(x))
+#  elif defined(__cplusplus) && __cplusplus >= 201103L
+#    include <cmath> // it must include constexpr bool isinf(double);
 #  else
 RUBY_EXTERN int isinf(double);
 #  endif
@@ -170,7 +172,11 @@ RUBY_EXTERN int isinf(double);
 
 #ifndef isnan
 # ifndef HAVE_ISNAN
+#  if defined(__cplusplus) && __cplusplus >= 201103L
+#    include <cmath> // it must include constexpr bool isnan(double);
+#  else
 RUBY_EXTERN int isnan(double);
+#  endif
 # endif
 #endif
 
diff --git a/version.h b/version.h
index 9cdb62a503..ceeed666d9 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.4.5"
 #define RUBY_RELEASE_DATE "2018-07-30"
-#define RUBY_PATCHLEVEL 306
+#define RUBY_PATCHLEVEL 307
 
 #define RUBY_RELEASE_YEAR 2018
 #define RUBY_RELEASE_MONTH 7