diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 744360c769..6aa93b5ff7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -5018,7 +5018,7 @@ BootStrapXLOG(void)
 	record->xl_rmid = RM_XLOG_ID;
 	recptr += SizeOfXLogRecord;
 	/* fill the XLogRecordDataHeaderShort struct */
-	*(recptr++) = XLR_BLOCK_ID_DATA_SHORT;
+	*(recptr++) = (char)XLR_BLOCK_ID_DATA_SHORT;
 	*(recptr++) = sizeof(checkPoint);
 	memcpy(recptr, &checkPoint, sizeof(checkPoint));
 	recptr += sizeof(checkPoint);
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 03b05f937f..ea8e915029 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -739,7 +739,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 	if ((curinsert_flags & XLOG_INCLUDE_ORIGIN) &&
 		replorigin_session_origin != InvalidRepOriginId)
 	{
-		*(scratch++) = XLR_BLOCK_ID_ORIGIN;
+		*(scratch++) = (char)XLR_BLOCK_ID_ORIGIN;
 		memcpy(scratch, &replorigin_session_origin, sizeof(replorigin_session_origin));
 		scratch += sizeof(replorigin_session_origin);
 	}
@@ -749,13 +749,13 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 	{
 		if (mainrdata_len > 255)
 		{
-			*(scratch++) = XLR_BLOCK_ID_DATA_LONG;
+			*(scratch++) = (char)XLR_BLOCK_ID_DATA_LONG;
 			memcpy(scratch, &mainrdata_len, sizeof(uint32));
 			scratch += sizeof(uint32);
 		}
 		else
 		{
-			*(scratch++) = XLR_BLOCK_ID_DATA_SHORT;
+			*(scratch++) = (char)XLR_BLOCK_ID_DATA_SHORT;
 			*(scratch++) = (uint8) mainrdata_len;
 		}
 		rdt_datas_last->next = mainrdata_head;
diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 27bd9b04e7..ed6968d605 100644
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -1095,7 +1095,7 @@ WriteEmptyXLOG(void)
 	record->xl_rmid = RM_XLOG_ID;
 
 	recptr += SizeOfXLogRecord;
-	*(recptr++) = XLR_BLOCK_ID_DATA_SHORT;
+	*(recptr++) = (char)XLR_BLOCK_ID_DATA_SHORT;
 	*(recptr++) = sizeof(CheckPoint);
 	memcpy(recptr, &ControlFile.checkPointCopy,
 		   sizeof(CheckPoint));
diff --git a/src/include/port.h b/src/include/port.h
index f4546016e7..0f014b72b6 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -395,11 +395,22 @@ extern double rint(double x);
 extern int	inet_aton(const char *cp, struct in_addr * addr);
 #endif
 
-#if !HAVE_DECL_STRLCAT
+/*
+ * Unfortunately in case of strlcat and strlcpy we can't trust tests
+ * executed by Autotools if Clang > 3.6 is used. Clang manages to compile
+ * a program that shouldn't compile which causes wrong values of
+ * HAVE_DECL_STRLCAT and HAVE_DECL_STRLCPY. More details could be found here:
+ *
+ * http://lists.llvm.org/pipermail/cfe-dev/2016-March/048126.html
+ *
+ * This is no doubt a dirty hack but apparently alternative solutions are
+ * not much better.
+ */
+#if !HAVE_DECL_STRLCAT || defined(__clang__)
 extern size_t strlcat(char *dst, const char *src, size_t siz);
 #endif
 
-#if !HAVE_DECL_STRLCPY
+#if !HAVE_DECL_STRLCPY || defined(__clang__)
 extern size_t strlcpy(char *dst, const char *src, size_t siz);
 #endif