diff --git a/src/OpenFOAM/primitives/Tensor/tensor/tensor.C b/src/OpenFOAM/primitives/Tensor/tensor/tensor.C
index 1b9dcb3a95d41082525d6b9319bf4c280291330a..7ec9702310a3ac0719ba486ea543f5a2d1680ce4 100644
--- a/src/OpenFOAM/primitives/Tensor/tensor/tensor.C
+++ b/src/OpenFOAM/primitives/Tensor/tensor/tensor.C
@@ -150,7 +150,7 @@ Foam::vector Foam::eigenValues(const tensor& t)
             if (R2 < Q3)
             {
                 scalar sqrtQ = sqrt(Q);
-                scalar theta = acos(R/(Q*sqrtQ));
+                scalar theta = acos(min(1.0, max(-1.0, R/(Q*sqrtQ))));
 
                 scalar m2SqrtQ = -2*sqrtQ;
                 scalar aBy3 = a/3;
@@ -345,7 +345,7 @@ Foam::vector Foam::eigenValues(const symmTensor& t)
             if (R2 < Q3)
             {
                 scalar sqrtQ = sqrt(Q);
-                scalar theta = acos(R/(Q*sqrtQ));
+                scalar theta = acos(min(1.0, max(-1.0, R/(Q*sqrtQ))));
 
                 scalar m2SqrtQ = -2*sqrtQ;
                 scalar aBy3 = a/3;