diff --git a/libvips/foreign/magick2vips.c b/libvips/foreign/magick2vips.c
index 768b4447..ae3d4e5f 100644
--- a/libvips/foreign/magick2vips.c
+++ b/libvips/foreign/magick2vips.c
@@ -109,7 +109,7 @@
 /* And this used to be UseHDRI.
  */
 #if MAGICKCORE_HDRI_SUPPORT
-#  define UseHDRI=1
+#  define UseHDRI 1
 #endif
 
 /* What we track during a read call.