diff --git a/adpcm-xq.c b/adpcm-xq.c
index 91d57cb..4e100c9 100644
--- a/adpcm-xq.c
+++ b/adpcm-xq.c
@@ -218,7 +218,7 @@ static double strtod_hexfree (const char *nptr, char **endptr)
     const char *sptr = nptr;
 
     // skip past any leading whitespace and possibly a sign
-    while isspace (*sptr) sptr++;
+    while (isspace (*sptr)) sptr++;
     if (*sptr == '+' || *sptr == '-') sptr++;
 
     // if hex detected ("0x" or "0X"), return 0.0 and end at the X