diff --git a/Python/pymath.c b/Python/pymath.c
index 7c00106..5cf61ab 100644
--- a/Python/pymath.c
+++ b/Python/pymath.c
@@ -35,6 +35,8 @@
 #endif /* HAVE_COPYSIGN */
 
 #ifndef HAVE_LOG1P
+#include <float.h>
+
 double
 log1p(double x)
 {