diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 271a2c3e481..fecf6f2d1ce 100644
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -44,6 +44,7 @@
 #include "pg_backup_archiver.h"
 #include "pg_backup_db.h"
 #include "pg_backup_utils.h"
+#include "pgtar.h"
 
 #define TEXT_DUMP_HEADER "--\n-- PostgreSQL database dump\n--\n\n"
 #define TEXT_DUMPALL_HEADER "--\n-- PostgreSQL database cluster dump\n--\n\n"
@@ -2372,7 +2373,7 @@ _discoverArchiveFormat(ArchiveHandle *AH)
 		}
 
 		if (!isValidTarHeader(AH->lookahead))
-			pg_fatal("input file does not appear to be a valid archive");
+			pg_fatal("input file does not appear to be a valid tar archive");
 
 		AH->format = archTar;
 	}
diff --git a/src/bin/pg_dump/pg_backup_archiver.h b/src/bin/pg_dump/pg_backup_archiver.h
index 365073b3eae..9c3aca6543a 100644
--- a/src/bin/pg_dump/pg_backup_archiver.h
+++ b/src/bin/pg_dump/pg_backup_archiver.h
@@ -465,8 +465,6 @@ extern void InitArchiveFmt_Null(ArchiveHandle *AH);
 extern void InitArchiveFmt_Directory(ArchiveHandle *AH);
 extern void InitArchiveFmt_Tar(ArchiveHandle *AH);
 
-extern bool isValidTarHeader(char *header);
-
 extern void ReconnectToServer(ArchiveHandle *AH, const char *dbname);
 extern void IssueCommandPerBlob(ArchiveHandle *AH, TocEntry *te,
 								const char *cmdBegin, const char *cmdEnd);
diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c
index d94d0de2a5d..a3879410c94 100644
--- a/src/bin/pg_dump/pg_backup_tar.c
+++ b/src/bin/pg_dump/pg_backup_tar.c
@@ -984,31 +984,6 @@ tarPrintf(TAR_MEMBER *th, const char *fmt,...)
 	return (int) cnt;
 }
 
-bool
-isValidTarHeader(char *header)
-{
-	int			sum;
-	int			chk = tarChecksum(header);
-
-	sum = read_tar_number(&header[TAR_OFFSET_CHECKSUM], 8);
-
-	if (sum != chk)
-		return false;
-
-	/* POSIX tar format */
-	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar\0", 6) == 0 &&
-		memcmp(&header[TAR_OFFSET_VERSION], "00", 2) == 0)
-		return true;
-	/* GNU tar format */
-	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar  \0", 8) == 0)
-		return true;
-	/* not-quite-POSIX format written by pre-9.3 pg_dump */
-	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar00\0", 8) == 0)
-		return true;
-
-	return false;
-}
-
 /* Given the member, write the TAR header & copy the file */
 static void
 _tarAddFile(ArchiveHandle *AH, TAR_MEMBER *th)
diff --git a/src/fe_utils/astreamer_tar.c b/src/fe_utils/astreamer_tar.c
index 3b094fc0328..8fa3329237d 100644
--- a/src/fe_utils/astreamer_tar.c
+++ b/src/fe_utils/astreamer_tar.c
@@ -260,7 +260,8 @@ astreamer_tar_parser_content(astreamer *streamer, astreamer_member *member,
  * Parse a file header within a tar stream.
  *
  * The return value is true if we found a file header and passed it on to the
- * next astreamer; it is false if we have reached the archive trailer.
+ * next astreamer; it is false if we have found the archive trailer.
+ * We throw error if we see invalid data.
  */
 static bool
 astreamer_tar_header(astreamer_tar_parser *mystreamer)
@@ -289,6 +290,12 @@ astreamer_tar_header(astreamer_tar_parser *mystreamer)
 	if (!has_nonzero_byte)
 		return false;
 
+	/*
+	 * Verify that we have a reasonable-looking header.
+	 */
+	if (!isValidTarHeader(buffer))
+		pg_fatal("input file does not appear to be a valid tar archive");
+
 	/*
 	 * Parse key fields out of the header.
 	 */
diff --git a/src/include/pgtar.h b/src/include/pgtar.h
index eb93bdef5c4..55b8c7c77a4 100644
--- a/src/include/pgtar.h
+++ b/src/include/pgtar.h
@@ -68,7 +68,8 @@ extern enum tarError tarCreateHeader(char *h, const char *filename,
 									 time_t mtime);
 extern uint64 read_tar_number(const char *s, int len);
 extern void print_tar_number(char *s, int len, uint64 val);
-extern int	tarChecksum(char *header);
+extern int	tarChecksum(const char *header);
+extern bool isValidTarHeader(const char *header);
 
 /*
  * Compute the number of padding bytes required for an entry in a tar
diff --git a/src/port/tar.c b/src/port/tar.c
index 592b4fb7b0f..db462b90292 100644
--- a/src/port/tar.c
+++ b/src/port/tar.c
@@ -87,7 +87,7 @@ read_tar_number(const char *s, int len)
  * be 512 bytes, per the tar standard.
  */
 int
-tarChecksum(char *header)
+tarChecksum(const char *header)
 {
 	int			i,
 				sum;
@@ -104,6 +104,35 @@ tarChecksum(char *header)
 	return sum;
 }
 
+/*
+ * Check validity of a tar header (assumed to be 512 bytes long).
+ * We verify the checksum and the magic number / version.
+ */
+bool
+isValidTarHeader(const char *header)
+{
+	int			sum;
+	int			chk = tarChecksum(header);
+
+	sum = read_tar_number(&header[TAR_OFFSET_CHECKSUM], 8);
+
+	if (sum != chk)
+		return false;
+
+	/* POSIX tar format */
+	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar\0", 6) == 0 &&
+		memcmp(&header[TAR_OFFSET_VERSION], "00", 2) == 0)
+		return true;
+	/* GNU tar format */
+	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar  \0", 8) == 0)
+		return true;
+	/* not-quite-POSIX format written by pre-9.3 pg_dump */
+	if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar00\0", 8) == 0)
+		return true;
+
+	return false;
+}
+
 
 /*
  * Fill in the buffer pointed to by h with a tar format header. This buffer