1 files changed, 4 insertions, 0 deletions
diff --git a/missing.h b/missing.h
index f3339f3200..ac499bd7d7 100644
--- a/missing.h
+++ b/missing.h
@@ -60,7 +60,11 @@ extern double erfc _((double));
 #endif
 
 #ifndef HAVE_ISINF
+# if defined(HAVE_FINITE) && defined(HAVE_ISNAN)
+# define isinf(x) (!finite(x) && !isnan(x))
+# else
 extern int isinf _((double));
+# endif
 #endif
 
 #ifndef HAVE_ISNAN