diff --git a/doc/language_issues.en b/doc/language_issues.en
index a3cde9166..ee4eb0151 100644
--- a/doc/language_issues.en
+++ b/doc/language_issues.en
@@ -14,6 +14,7 @@ WARNING: translation string unused: Captive invalid_voucher
 WARNING: translation string unused: Captive ip
 WARNING: translation string unused: Captive logo_set
 WARNING: translation string unused: Captive nr
+WARNING: translation string unused: Captive please enter a coupon code
 WARNING: translation string unused: Captive time
 WARNING: translation string unused: Captive voactive
 WARNING: translation string unused: Captive voucher
diff --git a/html/cgi-bin/captive/index.cgi b/html/cgi-bin/captive/index.cgi
index 963b890e8..482ea9016 100755
--- a/html/cgi-bin/captive/index.cgi
+++ b/html/cgi-bin/captive/index.cgi
@@ -78,36 +78,42 @@ if ($cgiparams{'ACTION'} eq "SUBMIT") {
 	if ($settings{"AUTH"} eq "COUPON") {
 		&General::readhasharray($coupons, \%couponhash);
 
-		# Convert coupon input to uppercase
-		$cgiparams{'COUPON'} = uc $cgiparams{'COUPON'};
+		if ($cgiparams{'COUPON'}) {
+			# Convert coupon input to uppercase
+			$cgiparams{'COUPON'} = uc $cgiparams{'COUPON'};
 
-		# Walk through all valid coupons and find the right one
-		my $found = 0;
-		foreach my $coupon (keys %couponhash) {
-			if ($couponhash{$coupon}[1] eq $cgiparams{'COUPON'}) {
-				$found = 1;
+			# Walk through all valid coupons and find the right one
+			my $found = 0;
+			foreach my $coupon (keys %couponhash) {
+				if ($couponhash{$coupon}[1] eq $cgiparams{'COUPON'}) {
+					$found = 1;
 
-				# Copy expiry time
-				$clientshash{$key}[3] = $couponhash{$coupon}[2];
+					# Copy expiry time
+					$clientshash{$key}[3] = $couponhash{$coupon}[2];
 
-				# Save coupon code
-				$clientshash{$key}[4] = $cgiparams{'COUPON'};
+					# Save coupon code
+					$clientshash{$key}[4] = $cgiparams{'COUPON'};
 
-				# Copy coupon remark
-				$clientshash{$key}[5] = $couponhash{$coupon}[3];
+					# Copy coupon remark
+					$clientshash{$key}[5] = $couponhash{$coupon}[3];
 
-				# Delete used coupon
-				delete $couponhash{$coupon};
-				&General::writehasharray($coupons, \%couponhash);
+					# Delete used coupon
+					delete $couponhash{$coupon};
+					&General::writehasharray($coupons, \%couponhash);
 
-				last;
+					last;
+				}
 			}
-		}
 
-		if ($found == 1) {
-			&General::log("Captive", "Internet access granted via coupon ($clientshash{$key}[4]) for $ip_address until $clientshash{$key}[3]");
+			if ($found == 1) {
+				&General::log("Captive", "Internet access granted via coupon ($clientshash{$key}[4]) for $ip_address until $clientshash{$key}[3]");
+			} else {
+				$errormessage = $Lang::tr{"Captive invalid coupon"};
+			}
+
+		# No coupon given
 		} else {
-			$errormessage = $Lang::tr{"Captive invalid coupon"};
+			$errormessage = $Lang::tr{"Captive please enter a coupon code"};
 		}
 
 	# License
diff --git a/html/html/captive/template.html b/html/html/captive/template.html
index 504920c64..a15c9a3ff 100644
--- a/html/html/captive/template.html
+++ b/html/html/captive/template.html
@@ -38,7 +38,7 @@
 								<input type="hidden" name="url" value="<TMPL_VAR NAME="URL">">
 
 								<TMPL_IF NAME="COUPON">
-										<input class="form-text" type="text" name="COUPON">
+										<input class="form-text <TMPL_IF NAME="ERROR">error</TMPL_IF>" type="text" name="COUPON">
 										<input class="form-submit" type="submit"
 											value="<TMPL_VAR NAME="L_ACTIVATE">">
 								<TMPL_ELSE>
@@ -46,10 +46,16 @@
 											value="<TMPL_VAR NAME="L_GAIN_ACCESS">">
 								</TMPL_IF>
 
+								<TMPL_IF NAME="ERROR">
+									<p class="error">
+										<TMPL_VAR NAME="ERROR">
+									</p>
+								</TMPL_IF>
+
 								<TMPL_IF NAME="TERMS">
 									<div class="checkbox">
 										<label>
-											<input class="form-checkbox" type="checkbox">
+											<input class="form-checkbox <TMPL_IF NAME="ERROR">error</TMPL_IF>" type="checkbox">
 											<TMPL_VAR NAME="L_AGREE_TERMS">
 										</label>
 									</div>
diff --git a/langs/en/cgi-bin/en.pl b/langs/en/cgi-bin/en.pl
index e243f6bcb..f569f53b0 100644
--- a/langs/en/cgi-bin/en.pl
+++ b/langs/en/cgi-bin/en.pl
@@ -42,6 +42,7 @@
 'Captive noexpiretime' => 'No valid connection time range given',
 'Captive nolimit' => 'unlimited',
 'Captive nr' => 'Number',
+'Captive please enter a coupon code' => 'Please enter a coupon code',
 'Captive terms' => 'Terms &amp; Conditions',
 'Captive terms short' => 'T&Cs',
 'Captive time' => 'Access time post activation (hours)',