diff --git a/src/Time/sunpos.cxx b/src/Time/sunpos.cxx
index 81f2d87b1..0b1e03f59 100644
--- a/src/Time/sunpos.cxx
+++ b/src/Time/sunpos.cxx
@@ -341,6 +341,12 @@ void fgUpdateSunPos( void ) {
     dot = sgScalarProductVec3( surface_to_sun, v->get_surface_south() );
     // cout << "  Dot product = " << dot << endl;
 
+    if (dot > 1) {
+        SG_LOG( SG_ASTRO, SG_WARN,
+                "Dot product  = " << dot << " is greater than 1.0" );
+        dot = 1.0;
+    }
+
     if ( east_dot >= 0 ) {
 	l->set_sun_rotation( acos(dot) );
     } else {