diff --git a/prism/src/explicit/ConstructModel.java b/prism/src/explicit/ConstructModel.java
index 19010969..5017f960 100644
--- a/prism/src/explicit/ConstructModel.java
+++ b/prism/src/explicit/ConstructModel.java
@@ -142,7 +142,7 @@ public class ConstructModel extends PrismComponent
 		VarList varList = modulesFile.createVarList();
 		if (varList.containsUnboundedVariables())
 			mainLog.printWarning("Model contains one or more unbounded variables: model construction may not terminate");
-		
+
 		// Starting reachability...
 		mainLog.print("\nComputing reachable states...");
 		mainLog.flush();
@@ -170,6 +170,10 @@ public class ConstructModel extends PrismComponent
 			case CTMDP:
 				modelSimple = ctmdp = new CTMDPSimple();
 				break;
+			case STPG:
+			case SMG:
+			case PTA:
+				throw new PrismException("Model construction not supported for " + modelType + "s");
 			}
 		}
 
@@ -213,8 +217,8 @@ public class ConstructModel extends PrismComponent
 			// Look at each outgoing choice in turn
 			nc = engine.getNumChoices();
 			for (i = 0; i < nc; i++) {
-
-				if (!justReach && (modelType == ModelType.MDP || modelType == ModelType.CTMDP)) {
+				// For nondet models, collect transitions in a Distribution
+				if (!justReach && modelType.nondeterministic()) {
 					distr = new Distribution();
 				}
 				// Look at each transition in the choice
@@ -242,14 +246,17 @@ public class ConstructModel extends PrismComponent
 							ctmc.addToProbability(src, dest, engine.getTransitionProbability(i, j));
 							break;
 						case MDP:
-							distr.add(dest, engine.getTransitionProbability(i, j));
-							break;
 						case CTMDP:
 							distr.add(dest, engine.getTransitionProbability(i, j));
 							break;
+						case STPG:
+						case SMG:
+						case PTA:
+							throw new PrismException("Model construction not supported for " + modelType + "s");
 						}
 					}
 				}
+				// For nondet models, add collated transition to model 
 				if (!justReach) {
 					if (modelType == ModelType.MDP) {
 						if (distinguishActions) {
@@ -319,6 +326,10 @@ public class ConstructModel extends PrismComponent
 			case CTMDP:
 				model = sort ? new CTMDPSimple(ctmdp, permut) : mdp;
 				break;
+			case STPG:
+			case SMG:
+			case PTA:
+				throw new PrismException("Model construction not supported for " + modelType + "s");
 			}
 			model.setStatesList(statesList);
 			model.setConstantValues(new Values(modulesFile.getConstantValues()));