diff --git a/unsupported/Eigen/src/NonLinear/HybridNonLinearSolver.h b/unsupported/Eigen/src/NonLinear/HybridNonLinearSolver.h
index c854f947a..fa68ae929 100644
--- a/unsupported/Eigen/src/NonLinear/HybridNonLinearSolver.h
+++ b/unsupported/Eigen/src/NonLinear/HybridNonLinearSolver.h
@@ -114,11 +114,11 @@ HybridNonLinearSolver<FunctorType,Scalar>::solve(
     /* Local variables */
     int i, j, l, iwa[1];
     Scalar sum;
-    int sing;
+    bool sing;
     int iter;
     Scalar temp;
     Scalar delta;
-    int jeval;
+    bool jeval;
     int ncsuc;
     Scalar ratio;
     Scalar fnorm;
@@ -434,12 +434,12 @@ HybridNonLinearSolver<FunctorType,Scalar>::solveNumericalDiff(
     /* Local variables */
     int i, j, l, iwa[1];
     Scalar sum;
-    int sing;
+    bool sing;
     int iter;
     Scalar temp;
     int msum;
     Scalar delta;
-    int jeval;
+    bool jeval;
     int ncsuc;
     Scalar ratio;
     Scalar fnorm;
diff --git a/unsupported/Eigen/src/NonLinear/LevenbergMarquardt.h b/unsupported/Eigen/src/NonLinear/LevenbergMarquardt.h
index 064256e2f..0ce2d83b9 100644
--- a/unsupported/Eigen/src/NonLinear/LevenbergMarquardt.h
+++ b/unsupported/Eigen/src/NonLinear/LevenbergMarquardt.h
@@ -706,7 +706,8 @@ LevenbergMarquardt<FunctorType,Scalar>::minimizeOptimumStorage(
     /* Local variables */
     int i, j, l;
     Scalar par, sum;
-    int sing, iter;
+    int iter;
+    bool sing;
     Scalar temp, temp1, temp2;
     Scalar delta;
     Scalar ratio;
diff --git a/unsupported/Eigen/src/NonLinear/r1updt.h b/unsupported/Eigen/src/NonLinear/r1updt.h
index 7d9d13e67..b3ae90bd8 100644
--- a/unsupported/Eigen/src/NonLinear/r1updt.h
+++ b/unsupported/Eigen/src/NonLinear/r1updt.h
@@ -1,6 +1,6 @@
 
 template <typename Scalar>
-void ei_r1updt(int m, int n, Scalar *s, int /* ls */, const Scalar *u, Scalar *v, Scalar *w, int *sing)
+void ei_r1updt(int m, int n, Scalar *s, int /* ls */, const Scalar *u, Scalar *v, Scalar *w, bool *sing)
 {
     /* Local variables */
     int i, j, l, jj, nm1;