diff --git a/src/org/sosy_lab/java_smt/solvers/mathsat5/Mathsat5AbstractProver.java b/src/org/sosy_lab/java_smt/solvers/mathsat5/Mathsat5AbstractProver.java
index 68e5717291..5facef977b 100644
--- a/src/org/sosy_lab/java_smt/solvers/mathsat5/Mathsat5AbstractProver.java
+++ b/src/org/sosy_lab/java_smt/solvers/mathsat5/Mathsat5AbstractProver.java
@@ -112,13 +112,13 @@ private <T> T exec(Callable<T> closure) throws SolverException, InterruptedExcep
   }
 
   @Override
-  public synchronized boolean isUnsat() throws InterruptedException, SolverException {
+  public boolean isUnsat() throws InterruptedException, SolverException {
     Preconditions.checkState(!closed);
     return exec(() -> !msat_check_sat(curEnv));
   }
 
   @Override
-  public synchronized boolean isUnsatWithAssumptions(Collection<BooleanFormula> pAssumptions)
+  public boolean isUnsatWithAssumptions(Collection<BooleanFormula> pAssumptions)
       throws SolverException, InterruptedException {
     Preconditions.checkState(!closed);
     checkForLiterals(pAssumptions);
@@ -238,7 +238,7 @@ protected boolean isClosed() {
   }
 
   @Override
-  public synchronized <T> T allSat(AllSatCallback<T> callback, List<BooleanFormula> important)
+  public <T> T allSat(AllSatCallback<T> callback, List<BooleanFormula> important)
       throws InterruptedException, SolverException {
     Preconditions.checkState(!closed);
     checkGenerateAllSat();