1diff --git a/third_party/lcms/src/cmsplugin.c b/third_party/lcms/src/cmsplugin.c
2index b95befb..4ba998b 100644
3--- a/third_party/lcms/src/cmsplugin.c
4+++ b/third_party/lcms/src/cmsplugin.c
5@@ -182,7 +182,9 @@ cmsBool CMSEXPORT  _cmsReadFloat32Number(cmsIOHANDLER* io, cmsFloat32Number* n)
6         if (isnan(*n))
7             return FALSE;
8     }
9-    return TRUE;
10+
11+    // fpclassify() required by C99
12+    return (fpclassify(*n) == FP_ZERO) || (fpclassify(*n) == FP_NORMAL);
13 }
14 
15 
16