diff --git a/include/types/checks.h b/include/types/checks.h
index 2205633..30f7d75 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -253,11 +253,12 @@
 };
 
 enum tcpcheck_expect_type {
-	TCPCHK_EXPECT_UNDEF = 0, /* Match is not used. */
-	TCPCHK_EXPECT_STRING, /* Matches a string. */
-	TCPCHK_EXPECT_REGEX, /* Matches a regular pattern. */
+	TCPCHK_EXPECT_UNDEF = 0,    /* Match is not used. */
+	TCPCHK_EXPECT_STRING,       /* Matches a string. */
+	TCPCHK_EXPECT_REGEX,        /* Matches a regular pattern. */
 	TCPCHK_EXPECT_REGEX_BINARY, /* Matches a regular pattern on a hex-encoded text. */
-	TCPCHK_EXPECT_BINARY, /* Matches a binary sequence. */
+	TCPCHK_EXPECT_BINARY,       /* Matches a binary sequence. */
+	TCPCHK_EXPECT_CUSTOM,       /* Execute a custom function. */
 };
 
 struct tcpcheck_expect {
@@ -265,6 +266,9 @@
 	union {
 		char *string;           /* Matching a literal string / binary anywhere in the response. */
 		struct my_regex *regex; /* Matching a regex pattern. */
+
+		/* custom function to eval epxect rule */
+		enum tcpcheck_eval_ret (*custom)(struct check *, struct tcpcheck_rule *, int);
 	};
 	struct tcpcheck_rule *head;     /* first expect of a chain. */
 	int length;                     /* Size in bytes of the pattern referenced by string / binary. */
diff --git a/src/checks.c b/src/checks.c
index 6a28b54..c6bced8 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -664,6 +664,9 @@
 				case TCPCHK_EXPECT_REGEX_BINARY:
 					chunk_appendf(chk, " (expect binary regex)");
 					break;
+				case TCPCHK_EXPECT_CUSTOM:
+					chunk_appendf(chk, " (expect custom function)");
+					break;
 				case TCPCHK_EXPECT_UNDEF:
 					chunk_appendf(chk, " (undefined expect!)");
 					break;
@@ -2803,6 +2806,9 @@
 			}
 		}
 		break;
+	case TCPCHK_EXPECT_CUSTOM:
+		chunk_appendf(msg, " (custom function) at step %d", tcpcheck_get_step_id(check, rule));
+		break;
 	case TCPCHK_EXPECT_UNDEF:
 		/* Should never happen. */
 		return;
@@ -3193,6 +3199,10 @@
 		else
 			match = regex_exec2(expect->regex, b_head(&trash), MIN(b_data(&trash), b_size(&trash)-1));
 		break;
+	case TCPCHK_EXPECT_CUSTOM:
+		if (expect->custom)
+			ret = expect->custom(check, rule, last_read);
+		goto out;
 	case TCPCHK_EXPECT_UNDEF:
 		/* Should never happen. */
 		ret = TCPCHK_EVAL_STOP;
@@ -3540,6 +3550,7 @@
 		case TCPCHK_EXPECT_REGEX_BINARY:
 			regex_free(rule->expect.regex);
 			break;
+		case TCPCHK_EXPECT_CUSTOM:
 		case TCPCHK_EXPECT_UNDEF:
 			break;
 		}
@@ -4676,8 +4687,8 @@
 	int inverse = 0, with_capture = 0;
 
 	str = on_success_msg = on_error_msg = comment = pattern = NULL;
-	if (!*(args[cur_arg+1]) || !*(args[cur_arg+2])) {
-		memprintf(errmsg, "expects a pattern (type+string) as arguments");
+	if (!*(args[cur_arg+1])) {
+		memprintf(errmsg, "expects at least a matching pattern as arguments");
 		goto error;
 	}
 
@@ -4730,6 +4741,17 @@
 			cur_arg++;
 			pattern = args[cur_arg];
 		}
+		else if (strcmp(args[cur_arg], "custom") == 0) {
+			if (in_pattern) {
+				memprintf(errmsg, "[!] not supported with '%s'", args[cur_arg]);
+				goto error;
+			}
+			if (type != TCPCHK_EXPECT_UNDEF) {
+				memprintf(errmsg, "only on pattern expected");
+				goto error;
+			}
+			type = TCPCHK_EXPECT_CUSTOM;
+		}
 		else if (strcmp(args[cur_arg], "comment") == 0) {
 			if (in_pattern) {
 				memprintf(errmsg, "[!] not supported with '%s'", args[cur_arg]);
@@ -4941,6 +4963,9 @@
 		if (!chk->expect.regex)
 			goto error;
 		break;
+	case TCPCHK_EXPECT_CUSTOM:
+		chk->expect.custom = NULL; /* Must be defined by the caller ! */
+		break;
 	case TCPCHK_EXPECT_UNDEF:
 		free(chk);
 		memprintf(errmsg, "pattern not found");