diff --git a/library/modules/Materials.cpp b/library/modules/Materials.cpp
index cc9102ae5..2682f57bf 100644
--- a/library/modules/Materials.cpp
+++ b/library/modules/Materials.cpp
@@ -355,6 +355,7 @@ bool MaterialInfo::matches(const df::dfhack_material_category &cat)
     TEST(glass, IS_GLASS);
     if (cat.bits.clay && linear_index(material->reaction_product.id, std::string("FIRED_MAT")) >= 0)
         return true;
+    return false;
 }
 
 #undef TEST