diff --git a/indra/newview/fsposeranimator.cpp b/indra/newview/fsposeranimator.cpp
index 7c79b85031..7e7442ebd5 100644
--- a/indra/newview/fsposeranimator.cpp
+++ b/indra/newview/fsposeranimator.cpp
@@ -643,7 +643,7 @@ bool FSPoserAnimator::getFreeRotationAtAandB(const LLVector3& posA, const LLVect
     rotationAxis.normalize();
 
     F32 angle = asin(lengthMove / lengthAC);
-    if (std::isnan(angle))
+    if (llisnan(angle))
         return false;
 
     changeAtA = LLQuaternion(angle, rotationAxis);
@@ -694,7 +694,7 @@ LLQuaternion FSPoserAnimator::getAbcFrameRotation(const LLVector3& posA, const L
     LLVector3 rotationAxis = vectorAC % changeAtC;
     rotationAxis.normalize();
 
-    if (std::isnan(angle))
+    if (llisnan(angle))
         angle = 0.f;
 
     return LLQuaternion(angle, rotationAxis);