diff --git a/libvips/mosaicing/matrixinvert.c b/libvips/mosaicing/matrixinvert.c
index 53592f56..157773e2 100644
--- a/libvips/mosaicing/matrixinvert.c
+++ b/libvips/mosaicing/matrixinvert.c
@@ -42,6 +42,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <math.h>
 
 #include <vips/vips.h>