diff --git a/doomsday/sdk/libcore/include/de/core/slope.h b/doomsday/sdk/libcore/include/de/core/slope.h
index aeeb475150..191c194566 100644
--- a/doomsday/sdk/libcore/include/de/core/slope.h
+++ b/doomsday/sdk/libcore/include/de/core/slope.h
@@ -22,7 +22,11 @@
 
 namespace de {
 
-struct Slope
+/**
+ * Combination of a yaw angle and Z slope at an XY distance of 1.0 units.
+ * @ingroup math
+ */
+DENG2_PUBLIC struct Slope
 {
     float angle; // radians
     float slope;