diff --git a/lib/sfio/sfdlen.c b/lib/sfio/sfdlen.c
index 2b4f8b0a3..3b2c75066 100644
--- a/lib/sfio/sfdlen.c
+++ b/lib/sfio/sfdlen.c
@@ -13,6 +13,8 @@
 
 #include	"sfhdr.h"
 
+#include <math.h>
+
 /*	Return the length of a double value if coded in a portable format
 **
 **	Written by Kiem-Phong Vo
diff --git a/lib/sfio/sfgetd.c b/lib/sfio/sfgetd.c
index 535b2cb9a..607681e60 100644
--- a/lib/sfio/sfgetd.c
+++ b/lib/sfio/sfgetd.c
@@ -13,6 +13,8 @@
 
 #include	"sfhdr.h"
 
+#include <math.h>
+
 /*	Read a portably coded double value
 **
 **	Written by Kiem-Phong Vo
diff --git a/lib/sfio/sfputd.c b/lib/sfio/sfputd.c
index 64ab9eaf3..a2dbd225c 100644
--- a/lib/sfio/sfputd.c
+++ b/lib/sfio/sfputd.c
@@ -14,6 +14,7 @@
 #include	"sfhdr.h"
 
 #include <float.h>
+#include <math.h>
 
 /*	Write out a floating point value in a portable format
 **