diff --git a/src/mesa/main/querymatrix.c b/src/mesa/main/querymatrix.c
index ca292aa0e89..a0969f6b9ff 100644
--- a/src/mesa/main/querymatrix.c
+++ b/src/mesa/main/querymatrix.c
@@ -71,7 +71,7 @@ fpclassify(double x)
 }
 
 #elif defined(__APPLE__) || defined(__CYGWIN__) || defined(__FreeBSD__) || \
-     (defined(__sun) && defined(__C99FEATURES__))
+     defined(__DragonFly__) || (defined(__sun) && defined(__C99FEATURES__))
 
 /* fpclassify is available. */