diff --git a/src/lib/libast/features/float b/src/lib/libast/features/float
index cadf8f201..d927bc167 100644
--- a/src/lib/libast/features/float
+++ b/src/lib/libast/features/float
@@ -993,6 +993,7 @@ tst	- -DSCAN=1 - -lm -DSTRTO=1 - -DMAC=1 - -DDIV=1 - -DEXP=1 - -DADD=1 - -DMPY=1
 	#include <stdio.h>
 	#include <sys/types.h>
 	#include <signal.h>
+	#include <string.h>
 	#if _hdr_float
 	#include <float.h>
 	#endif
@@ -1094,6 +1095,7 @@ tst	- -DSCAN=1 - -lm -DSTRTO=1 - -DMAC=1 - -DDIV=1 - -DEXP=1 - -DADD=1 - -DMPY=1
 		char*	e;
 	#endif
 
+	memset(&f, '\0', sizeof(f));
 	#if SCAN
 		if (sscanf(NAN, "%Lg", &f) != 1)
 			return 1;
@@ -1103,6 +1105,7 @@ tst	- -DSCAN=1 - -lm -DSTRTO=1 - -DMAC=1 - -DDIV=1 - -DEXP=1 - -DADD=1 - -DMPY=1
 			return 1;
 	#endif
 		list("ldbl", "nan", &f, sizeof(f));
+	memset(&f, '\0', sizeof(f));
 	#if SCAN
 		if (sscanf(INF, "%Lg", &f) != 1)
 			return 1;
diff --git a/src/lib/libast/sfio/sfcvt.c b/src/lib/libast/sfio/sfcvt.c
index a83b8ef89..8063a5f42 100644
--- a/src/lib/libast/sfio/sfcvt.c
+++ b/src/lib/libast/sfio/sfcvt.c
@@ -44,6 +44,7 @@ static char		*Zero = "0";
 #define isnan(n)	(fpclassify(n)==FP_NAN)
 #define isnanl(n)	(fpclassify(n)==FP_NAN)
 #else
+#error "This is an invalid test for NaN"
 #define isnan(n)	(memcmp((void*)&n,(void*)&_Sfdnan,sizeof(n))==0)
 #define isnanl(n)	(memcmp((void*)&n,(void*)&_Sflnan,sizeof(n))==0)
 #endif