diff --git a/org/qmckl_sherman_morrison_woodbury.org b/org/qmckl_sherman_morrison_woodbury.org
index a78002f..ef21226 100644
--- a/org/qmckl_sherman_morrison_woodbury.org
+++ b/org/qmckl_sherman_morrison_woodbury.org
@@ -16,7 +16,7 @@ Low- and high-level functions that use the Sherman-Morrison and Woodbury matrix
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
-#include <cmath>
+#include <math.h>
 #ifndef THRESHOLD
 #define THRESHOLD 1e-3
 #endif