diff --git a/build.gradle.kts b/build.gradle.kts
index da28832906..690154b7b0 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -10,7 +10,7 @@ buildscript {
 
 allprojects {
     group = "hu.bme.mit.inf.theta"
-    version = "2.5.0"
+    version = "2.5.1"
 
     apply(from = rootDir.resolve("gradle/shared-with-buildSrc/mirrors.gradle.kts"))
 }
diff --git a/subprojects/solver-z3/src/main/java/hu/bme/mit/theta/solver/z3/Z3TermTransformer.java b/subprojects/solver-z3/src/main/java/hu/bme/mit/theta/solver/z3/Z3TermTransformer.java
index d049fa8068..dcb8be42c1 100644
--- a/subprojects/solver-z3/src/main/java/hu/bme/mit/theta/solver/z3/Z3TermTransformer.java
+++ b/subprojects/solver-z3/src/main/java/hu/bme/mit/theta/solver/z3/Z3TermTransformer.java
@@ -16,6 +16,7 @@
 package hu.bme.mit.theta.solver.z3;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static hu.bme.mit.theta.common.Utils.head;
 import static hu.bme.mit.theta.common.Utils.tail;
@@ -117,6 +118,7 @@ public Expr<?> toExpr(final com.microsoft.z3.Expr term) {
 
 	public Expr<?> toFuncLitExpr(final FuncDecl funcDecl, final Model model,
 								 final List<Decl<?>> vars) {
+		checkNotNull(model, "Unsupported function '" + funcDecl.getName() + "' in Z3 back-transformation.");
 		final com.microsoft.z3.FuncInterp funcInterp = model.getFuncInterp(funcDecl);
 		final List<ParamDecl<?>> paramDecls = transformParams(vars, funcDecl.getDomain());
 		pushParams(vars, paramDecls);