diff --git a/programs/x509/cert_app.c b/programs/x509/cert_app.c
index 0096735bd..eb6414d9c 100644
--- a/programs/x509/cert_app.c
+++ b/programs/x509/cert_app.c
@@ -190,19 +190,17 @@ int main( int argc, char *argv[] )
 
     for( i = 1; i < argc; i++ )
     {
-        n = strlen( argv[i] );
-
-        for( j = 0; j < n; j++ )
-        {
-            if( argv[i][j] >= 'A' && argv[i][j] <= 'Z' )
-                argv[i][j] |= 0x20;
-        }
-
         p = argv[i];
         if( ( q = strchr( p, '=' ) ) == NULL )
             goto usage;
         *q++ = '\0';
 
+        for( j = 0; p + j < q; j++ )
+        {
+            if( argv[i][j] >= 'A' && argv[i][j] <= 'Z' )
+                argv[i][j] |= 0x20;
+        }
+
         if( strcmp( p, "mode" ) == 0 )
         {
             if( strcmp( q, "file" ) == 0 )