diff --git a/scan/scan_int.c b/scan/scan_int.c
index b881db2..c4e8a10 100644
--- a/scan/scan_int.c
+++ b/scan/scan_int.c
@@ -3,6 +3,6 @@
 unsigned int scan_int(const char* src,int* dest) {
   long l;
   register int len=scan_long(src,&l);
-  *dest=l;
+  if (len) *dest=l;
   return len;
 }
diff --git a/scan/scan_long.c b/scan/scan_long.c
index 53aef1c..8f2148d 100644
--- a/scan/scan_long.c
+++ b/scan/scan_long.c
@@ -5,7 +5,8 @@ unsigned int scan_long(const char *src,long *dest) {
   register long int l;
   register unsigned char c;
   int neg;
-  tmp=src; l=0; neg=0;
+  int ok;
+  tmp=src; l=0; ok=neg=0;
   switch (*tmp) {
   case '-': neg=1;
   case '+': ++tmp;
@@ -13,7 +14,8 @@ unsigned int scan_long(const char *src,long *dest) {
   while ((c=*tmp-'0')<10) {
     l=l*10+c;
     ++tmp;
+    ok=1;
   }
-  *dest=(neg?-l:l);
+  if (ok) *dest=(neg?-l:l);
   return tmp-src;
 }
diff --git a/scan/scan_longlong.c b/scan/scan_longlong.c
index 393d1b6..2d57328 100644
--- a/scan/scan_longlong.c
+++ b/scan/scan_longlong.c
@@ -6,7 +6,7 @@ unsigned int scan_longlong(const char* src,signed long long* dest) {
   char c=src[0];
   o=c=='-' || c=='+';
   if ((i=scan_ulonglong(src+o,&l))) {
-    *dest=c=='-'?-l:l;
+    if (i+o) *dest=c=='-'?-l:l;
     return i+o;
   } return 0;
 }
diff --git a/scan/scan_uint.c b/scan/scan_uint.c
index 33f8501..656bc33 100644
--- a/scan/scan_uint.c
+++ b/scan/scan_uint.c
@@ -24,7 +24,7 @@ unsigned int scan_uint(const char* src,unsigned int* dest) {
       l=n+c;
       ++tmp;
     }
-    *dest=l;
+    if (tmp-src) *dest=l;
     return tmp-src;
   }
 }
diff --git a/scan/scan_ulong.c b/scan/scan_ulong.c
index e11f564..5d38bc2 100644
--- a/scan/scan_ulong.c
+++ b/scan/scan_ulong.c
@@ -14,6 +14,6 @@ unsigned int scan_ulong(const char* src,unsigned long int* dest) {
     l=n+c;
     ++tmp;
   }
-  *dest=l;
+  if (tmp-src) *dest=l;
   return tmp-src;
 }
diff --git a/scan/scan_ulonglong.c b/scan/scan_ulonglong.c
index 6d53c58..3ef5ce5 100644
--- a/scan/scan_ulonglong.c
+++ b/scan/scan_ulonglong.c
@@ -14,6 +14,6 @@ unsigned int scan_ulonglong(const char *src,unsigned long long *dest) {
     l=n+c;
     ++tmp;
   }
-  *dest=l;
+  if (tmp-src) *dest=l;
   return tmp-src;
 }
diff --git a/scan/scan_ushort.c b/scan/scan_ushort.c
index 5fe76a3..483319b 100644
--- a/scan/scan_ushort.c
+++ b/scan/scan_ushort.c
@@ -24,7 +24,7 @@ unsigned int scan_ushort(const char* src,unsigned short* dest) {
       l=n+c;
       ++tmp;
     }
-    *dest=l;
+    if (tmp-src) *dest=l;
     return tmp-src;
   }
 }