diff --git a/.gitignore b/.gitignore
index 7f1f3ee..94d6982 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@ keyinfo
 famtool
 i2pbase64
 regaddr
+regaddralias
 routerinfo
 vain
 b33address
diff --git a/vanitygen.cpp b/vanitygen.cpp
index 1d65f8f..982d09d 100644
--- a/vanitygen.cpp
+++ b/vanitygen.cpp
@@ -73,7 +73,7 @@ static bool check_prefix(const char * buf)
 	unsigned short size_str=0;
 	while(*buf)
 	{
-		if(*buf < 48 || (*buf > 57 && *buf < 65) || (*buf > 64 && *buf < 94) || *buf > 125 || size_str > 52)
+		if(!((*buf > 49 && *buf < 56) || (*buf > 96 && *buf < 123)) || size_str > 52)
 			return false;
 		size_str++;
 		buf++;