diff --git a/src/utils/SkUnitMappers.cpp b/src/utils/SkUnitMappers.cpp
index 929447e..b2ab02b 100644
--- a/src/utils/SkUnitMappers.cpp
+++ b/src/utils/SkUnitMappers.cpp
@@ -7,6 +7,8 @@
  */
 #include "SkUnitMappers.h"
 
+SK_DEFINE_INST_COUNT(SkUnitMapper)
+
 SkDiscreteMapper::SkDiscreteMapper(int segments) {
     if (segments < 2) {
         fSegments = 0;