diff --git a/Source/Core/ZDoom/ModeldefParser.cs b/Source/Core/ZDoom/ModeldefParser.cs
index 8ce1fe2c..8e69d0a2 100755
--- a/Source/Core/ZDoom/ModeldefParser.cs
+++ b/Source/Core/ZDoom/ModeldefParser.cs
@@ -200,7 +200,7 @@ namespace CodeImp.DoomBuilder.ZDoom
 									foreach(var fs in mds.Frames[targetsprite])
 									{
 										// Sanity checks
-										if(fs.ModelIndex >= mds.ModelNames.Count || string.IsNullOrEmpty(mds.ModelNames[fs.ModelIndex]))
+										if (!mds.ModelNames.ContainsKey(fs.ModelIndex) || string.IsNullOrEmpty(mds.ModelNames[fs.ModelIndex]))
 										{
 											LogWarning("Model definition \"" + classname + "\", frame \"" + fs.SpriteName + " " + fs.FrameName + "\" references undefined model index " + fs.ModelIndex);
 											continue;