diff --git a/src/http_conv.c b/src/http_conv.c
index 93b748c..803d7bc 100644
--- a/src/http_conv.c
+++ b/src/http_conv.c
@@ -217,6 +217,7 @@
 /* This fetch url-decode any input string. */
 static int sample_conv_url_dec(const struct arg *args, struct sample *smp, void *private)
 {
+	int in_form = 0;
 	int len;
 
 	/* If the constant flag is set or if not size is available at
@@ -233,7 +234,11 @@
 
 	/* Add final \0 required by url_decode(), and convert the input string. */
 	smp->data.u.str.area[smp->data.u.str.data] = '\0';
-	len = url_decode(smp->data.u.str.area);
+
+	if (args && (args[0].type == ARGT_SINT))
+		in_form = !!args[0].data.sint;
+
+	len = url_decode(smp->data.u.str.area, in_form);
 	if (len < 0)
 		return 0;
 	smp->data.u.str.data = len;
@@ -332,7 +337,7 @@
 	{ "language",       sample_conv_q_preferred,  ARG2(1,STR,STR),  NULL,   SMP_T_STR,  SMP_T_STR},
 	{ "capture-req",    smp_conv_req_capture,     ARG1(1,SINT),     NULL,   SMP_T_STR,  SMP_T_STR},
 	{ "capture-res",    smp_conv_res_capture,     ARG1(1,SINT),     NULL,   SMP_T_STR,  SMP_T_STR},
-	{ "url_dec",        sample_conv_url_dec,      0,                NULL,   SMP_T_STR,  SMP_T_STR},
+	{ "url_dec",        sample_conv_url_dec,      ARG1(0,SINT),     NULL,   SMP_T_STR,  SMP_T_STR},
 	{ NULL, NULL, 0, 0, 0 },
 }};
 
diff --git a/src/standard.c b/src/standard.c
index 7fc4fd7..b593345 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -1731,8 +1731,12 @@
  * be shorter. If some forbidden characters are found, the conversion is
  * aborted, the string is truncated before the issue and a negative value is
  * returned, otherwise the operation returns the length of the decoded string.
+ * If the 'in_form' argument is non-nul the string is assumed to be part of
+ * an "application/x-www-form-urlencoded" encoded string, and the '+' will be
+ * turned to a space. If it's zero, this will only be done after a question
+ * mark ('?').
  */
-int url_decode(char *string)
+int url_decode(char *string, int in_form)
 {
 	char *in, *out;
 	int ret = -1;
@@ -1742,7 +1746,7 @@
 	while (*in) {
 		switch (*in) {
 		case '+' :
-			*out++ = ' ';
+			*out++ = in_form ? ' ' : *in;
 			break;
 		case '%' :
 			if (!ishex(in[1]) || !ishex(in[2]))
@@ -1750,6 +1754,9 @@
 			*out++ = (hex2i(in[1]) << 4) + hex2i(in[2]);
 			in += 2;
 			break;
+		case '?':
+			in_form = 1;
+			/* fall through */
 		default:
 			*out++ = *in;
 			break;
diff --git a/src/stats.c b/src/stats.c
index f2cb099..f2091bb 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -2918,7 +2918,7 @@
 				/* Ok, a value is found, we can mark the end of the key */
 				*value++ = '\0';
 			}
-			if (url_decode(key) < 0 || url_decode(value) < 0)
+			if (url_decode(key, 1) < 0 || url_decode(value, 1) < 0)
 				break;
 
 			/* Now we can check the key to see what to do */