diff --git a/lslopt/lslbasefuncs.py b/lslopt/lslbasefuncs.py
index fbb6b4c..20f7e18 100644
--- a/lslopt/lslbasefuncs.py
+++ b/lslopt/lslbasefuncs.py
@@ -399,7 +399,12 @@ def InternalTypecast(val, out, InList, f32):
             if match.group(1):
                 ret =  F32(float.fromhex(match.group(0)), f32)
             else:
-                ret = F32(float(match.group(0)), f32)
+                if match.group(0).lower() == '-nan':
+                    # (float)"-nan" produces NaN instead of Indet, even though
+                    # (vector)"<-nan,0,0>" produces <Indet, 0., 0.>. Go figure.
+                    ret = NaN
+                else:
+                    ret = F32(float(match.group(0)), f32)
             if not lslcommon.LSO and abs(ret) < 1.1754943508222875e-38:
                 # Mono doesn't return denormals when using (float)"val"
                 # (but it returns them when using (vector)"<val,...>")