diff --git a/Sources/Plasma/PubUtilLib/plInterp/plAnimTimeConvert.cpp b/Sources/Plasma/PubUtilLib/plInterp/plAnimTimeConvert.cpp
index 31970667..48b0667c 100644
--- a/Sources/Plasma/PubUtilLib/plInterp/plAnimTimeConvert.cpp
+++ b/Sources/Plasma/PubUtilLib/plInterp/plAnimTimeConvert.cpp
@@ -559,7 +559,7 @@ hsScalar plAnimTimeConvert::WorldToAnimTime(double wSecs)
 				{
 					float result = fmodf(secs - fLoopBegin, fLoopEnd - fLoopBegin) + fLoopBegin;
 					// if fLoopBegin == fLoopEnd == 0, result will not be a number
-					if (!isnan(result))
+					if (!_isnan(result))
 					{
 						secs = result;
 						wrapped = true;
@@ -583,7 +583,7 @@ hsScalar plAnimTimeConvert::WorldToAnimTime(double wSecs)
 				{
 					float result  = fLoopEnd - fmodf(fLoopEnd - secs, fLoopEnd - fLoopBegin);
 					// if fLoopBegin == fLoopEnd == 0, result will not be a number
-					if (!isnan(result))
+					if (!_isnan(result))
 					{
 						secs = result;
 						wrapped = true;