diff --git a/doomsday/plugins/wadmapconverter/src/id1map_load.cpp b/doomsday/plugins/wadmapconverter/src/id1map_load.cpp
index 0016d2ce1d..ada329607f 100644
--- a/doomsday/plugins/wadmapconverter/src/id1map_load.cpp
+++ b/doomsday/plugins/wadmapconverter/src/id1map_load.cpp
@@ -1596,8 +1596,6 @@ int LoadMap(MapLumpInfo* lumpInfos[NUM_MAPLUMP_TYPES])
 {
     DENG_ASSERT(lumpInfos);
 
-    memset(DENG_PLUGIN_GLOBAL(map), 0, sizeof(*DENG_PLUGIN_GLOBAL(map)));
-
     // Allocate the data structure arrays.
     map->vertexes =   (coord_t*)malloc(map->numVertexes * 2 * sizeof(*map->vertexes));
     map->lines    =   (mline_t*)malloc(map->numLines * sizeof(mline_t));
diff --git a/doomsday/plugins/wadmapconverter/src/wadmapconverter.cpp b/doomsday/plugins/wadmapconverter/src/wadmapconverter.cpp
index 6fc16cb88a..d7d0b0e49c 100644
--- a/doomsday/plugins/wadmapconverter/src/wadmapconverter.cpp
+++ b/doomsday/plugins/wadmapconverter/src/wadmapconverter.cpp
@@ -163,6 +163,7 @@ int ConvertMapHook(int hookType, int parm, void* context)
     collectMapLumps(lumpInfos, markerLump + 1 /*begin after the marker*/);
 
     // Do we recognise this format?
+    memset(DENG_PLUGIN_GLOBAL(map), 0, sizeof(*DENG_PLUGIN_GLOBAL(map)));
     recogniseMapFormat(lumpInfos);
     if(DENG_PLUGIN_GLOBAL(mapFormat) == MF_UNKNOWN)
     {