diff --git a/src/physics.F90 b/src/physics.F90
index 9ca59a9872..043bea6911 100644
--- a/src/physics.F90
+++ b/src/physics.F90
@@ -388,6 +388,13 @@ contains
 
     end if
 
+    ! Check p % mu to ensure it falls within the expected range
+    if (p % mu < -ONE) then
+      p % mu = -ONE
+    else if (p % mu > ONE) then
+      p % mu = ONE
+    end if
+
     ! Set event component
     p % event = EVENT_SCATTER