diff --git a/libraries/AP_Math/AP_Math.cpp b/libraries/AP_Math/AP_Math.cpp
index 0888414924..4476aec439 100644
--- a/libraries/AP_Math/AP_Math.cpp
+++ b/libraries/AP_Math/AP_Math.cpp
@@ -176,10 +176,10 @@ template <class T>
 T constrain_value(const T amt, const T low, const T high)
 {
     // the check for NaN as a float prevents propagation of floating point
-    // errors through any function that uses constrain_float(). The normal
+    // errors through any function that uses constrain_value(). The normal
     // float semantics already handle -Inf and +Inf
     if (isnan(amt)) {
-        return (low + high) * 0.5f;
+        return (low + high) / 2;
     }
 
     if (amt < low) {