diff --git a/NEWS b/NEWS
index e74147772c2..24acad4ddbc 100644
--- a/NEWS
+++ b/NEWS
@@ -21,6 +21,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-12186 (segfault copying/cloning a finalized HashContext).
     (MaxSem)
 
+- Intl:
+  . Fixed bug GH-12243 (segfault on IntlDateFormatter::construct).
+    (David Carlier)
+
 - SimpleXML:
   . Fixed bug GH-12170 (Can't use xpath with comments in SimpleXML). (nielsdos)
   . Fixed bug GH-12192 (SimpleXML infinite loop when getName() is called
diff --git a/ext/intl/dateformat/dateformat_create.cpp b/ext/intl/dateformat/dateformat_create.cpp
index 58867746ef0..50e0bd75b7e 100644
--- a/ext/intl/dateformat/dateformat_create.cpp
+++ b/ext/intl/dateformat/dateformat_create.cpp
@@ -99,7 +99,11 @@ static zend_result datefmt_ctor(INTERNAL_FUNCTION_PARAMETERS, zend_error_handlin
 	}
 	if (!INTL_UDATE_FMT_OK(time_type)) {
 		intl_error_set(NULL, U_ILLEGAL_ARGUMENT_ERROR, "datefmt_create: invalid time format style", 0);
-return FAILURE;
+		return FAILURE;
+	}
+	if (date_type == UDAT_PATTERN && time_type != UDAT_PATTERN) {
+		intl_error_set(NULL, U_ILLEGAL_ARGUMENT_ERROR, "datefmt_create: time format must be UDAT_PATTERN if date format is UDAT_PATTERN", 0);
+		return FAILURE;
 	}
 
 	INTL_CHECK_LOCALE_LEN_OR_FAILURE(locale_len);
diff --git a/ext/intl/tests/gh12243.phpt b/ext/intl/tests/gh12243.phpt
new file mode 100644
index 00000000000..80fb41032f3
--- /dev/null
+++ b/ext/intl/tests/gh12243.phpt
@@ -0,0 +1,24 @@
+--TEST--
+GitHub #12043 segfault with IntlDateFormatter::dateType where it equals to UDAT_PATTERN (icu 50) but
+IntldateFormatter::timeType needs to be set as such.
+--EXTENSIONS--
+intl
+--FILE--
+<?php
+
+$datetime = new \DateTime('2017-05-12 23:11:00 GMT+2');
+static $UDAT_PATTERN = -2;
+
+try {
+    new IntlDateFormatter(
+	    locale: 'en',
+	    dateType: $UDAT_PATTERN,
+	    timeType: 0,
+	    timezone: $datetime->getTimezone(),
+    );
+} catch (\IntlException $e) {
+    echo $e->getMessage();
+}
+
+--EXPECT--
+datefmt_create: time format must be UDAT_PATTERN if date format is UDAT_PATTERN: U_ILLEGAL_ARGUMENT_ERROR