diff --git a/src/filter.cpp b/src/filter.cpp
index 64ce318d..5a5d02c6 100644
--- a/src/filter.cpp
+++ b/src/filter.cpp
@@ -78,6 +78,13 @@ const FilterImp::FilterEntry *FilterImp::getFilter(int id)
 }
 
 
+bool Filter::isValidFilter(int filter_id)
+{
+    const FilterImp::FilterEntry * const fe = FilterImp::getFilter(filter_id);
+    return fe != NULL;
+}
+
+
 /*************************************************************************
 // high level API
 **************************************************************************/
diff --git a/src/filter.h b/src/filter.h
index 245ae99d..abd77218 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -61,6 +61,8 @@ public:
     void verifyUnfilter();
     bool scan(const upx_byte *buf, unsigned buf_len);
 
+    static bool isValidFilter(int filter_id);
+
 public:
     // Will be set by each call to filter()/unfilter().
     // Read-only afterwards.