diff --git a/mp/src/utils/common/mstristrip.cpp b/mp/src/utils/common/mstristrip.cpp
index 6a66de2f..9e611f94 100644
--- a/mp/src/utils/common/mstristrip.cpp
+++ b/mp/src/utils/common/mstristrip.cpp
@@ -867,7 +867,7 @@ public:
     int iFirstUsed;
     int iOrigIndex;
 
-    bool operator<(const SortEntry& rhs)
+    bool operator<(const SortEntry& rhs) const
     {
         return iFirstUsed < rhs.iFirstUsed;
     }
diff --git a/sp/src/utils/common/mstristrip.cpp b/sp/src/utils/common/mstristrip.cpp
index 6a66de2f..9e611f94 100644
--- a/sp/src/utils/common/mstristrip.cpp
+++ b/sp/src/utils/common/mstristrip.cpp
@@ -867,7 +867,7 @@ public:
     int iFirstUsed;
     int iOrigIndex;
 
-    bool operator<(const SortEntry& rhs)
+    bool operator<(const SortEntry& rhs) const
     {
         return iFirstUsed < rhs.iFirstUsed;
     }