diff --git a/prism/src/explicit/DTMCSimple.java b/prism/src/explicit/DTMCSimple.java
index ec92d2b2..3d5ecd89 100644
--- a/prism/src/explicit/DTMCSimple.java
+++ b/prism/src/explicit/DTMCSimple.java
@@ -145,8 +145,10 @@ public class DTMCSimple extends DTMCExplicit implements ModelSimple
 			// Parse first line to get num states
 			s = in.readLine();
 			lineNum = 1;
-			if (s == null)
+			if (s == null) {
+				in.close();
 				throw new PrismException("Missing first line of .tra file");
+			}
 			ss = s.split(" ");
 			n = Integer.parseInt(ss[0]);
 			// Initialise
diff --git a/prism/src/explicit/MDPSimple.java b/prism/src/explicit/MDPSimple.java
index 8531cb75..de3d8667 100644
--- a/prism/src/explicit/MDPSimple.java
+++ b/prism/src/explicit/MDPSimple.java
@@ -283,8 +283,10 @@ public class MDPSimple extends MDPExplicit implements ModelSimple
 			// Parse first line to get num states
 			s = in.readLine();
 			lineNum = 1;
-			if (s == null)
+			if (s == null) {
+				in.close();
 				throw new PrismException("Missing first line of .tra file");
+			}
 			ss = s.split(" ");
 			n = Integer.parseInt(ss[0]);
 			// Initialise
diff --git a/prism/src/explicit/MDPSparse.java b/prism/src/explicit/MDPSparse.java
index e6278dc7..315ae1cd 100644
--- a/prism/src/explicit/MDPSparse.java
+++ b/prism/src/explicit/MDPSparse.java
@@ -304,8 +304,10 @@ public class MDPSparse extends MDPExplicit
 			// Parse first line to get num states
 			s = in.readLine();
 			lineNum = 1;
-			if (s == null)
+			if (s == null) {
+				in.close();
 				throw new PrismException("Missing first line of .tra file");
+			}
 			ss = s.split(" ");
 			n = Integer.parseInt(ss[0]);
 			// Initialise
diff --git a/prism/src/explicit/Model.java b/prism/src/explicit/Model.java
index bc713171..d5e8f565 100644
--- a/prism/src/explicit/Model.java
+++ b/prism/src/explicit/Model.java
@@ -27,8 +27,9 @@
 package explicit;
 
 import java.io.File;
-import java.util.*;
-import java.util.Map.Entry;
+import java.util.BitSet;
+import java.util.Iterator;
+import java.util.List;
 
 import parser.State;
 import parser.Values;