diff --git a/src/cff/cffobjs.c b/src/cff/cffobjs.c
index cac4ac2..be75149 100644
--- a/src/cff/cffobjs.c
+++ b/src/cff/cffobjs.c
@@ -1063,14 +1063,32 @@
 #endif
     driver->no_stem_darkening = FALSE;
 
-    driver->darken_params[0] =  500;
-    driver->darken_params[1] =  400;
-    driver->darken_params[2] = 1000;
-    driver->darken_params[3] =  275;
-    driver->darken_params[4] = 1667;
-    driver->darken_params[5] =  275;
-    driver->darken_params[6] = 2333;
-    driver->darken_params[7] =    0;
+#ifndef CFF_CONFIG_OPTION_DARKENING_PARAMETERS
+#define CFF_CONFIG_OPTION_DARKENING_PARAMETERS 500,400, 1000,275, 1667,275, 2333,0
+#endif
+
+#define SET_DARKENING_PARAMETERS0(x1,y1,x2,y2,x3,y3,x4,y4) \
+    do { \
+    /* Checks copied from cffdrivr:cff_property_set(). */ \
+    typedef int static_assert_darkening_parameters[ \
+         ( x1 < 0   || x2 < 0   || x3 < 0   || x4 < 0   || \
+           y1 < 0   || y2 < 0   || y3 < 0   || y4 < 0   || \
+           x1 > x2  || x2 > x3  || x3 > x4              || \
+           y1 > 500 || y2 > 500 || y3 > 500 || y4 > 500 ) ? -1 : +1]; \
+    driver->darken_params[0] = x1; \
+    driver->darken_params[1] = y1; \
+    driver->darken_params[2] = x2; \
+    driver->darken_params[3] = y2; \
+    driver->darken_params[4] = x3; \
+    driver->darken_params[5] = y3; \
+    driver->darken_params[6] = x4; \
+    driver->darken_params[7] = y4; \
+    } while (0);
+#define SET_DARKENING_PARAMETERS(params) SET_DARKENING_PARAMETERS0(params)
+
+    SET_DARKENING_PARAMETERS(CFF_CONFIG_OPTION_DARKENING_PARAMETERS);
+
+#undef SET_DARKENING_PARAMETERS
 
     return FT_Err_Ok;
   }