diff --git a/configure b/configure
index 4b8229e..04d59bc 100755
--- a/configure
+++ b/configure
@@ -3725,7 +3725,11 @@ case ${wal_segsize} in
  16) ;;
  32) ;;
  64) ;;
-  *) as_fn_error $? "Invalid WAL segment size. Allowed values are 1,2,4,8,16,32,64." "$LINENO" 5
+ 128) ;;
+ 256) ;;
+ 512) ;;
+ 1024) ;;
+  *) as_fn_error $? "Invalid WAL segment size. Allowed values are 1,2,4,8,16,32,64,128,256,512,1024." "$LINENO" 5
 esac
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: ${wal_segsize}MB" >&5
 $as_echo "${wal_segsize}MB" >&6; }
diff --git a/configure.in b/configure.in
index 6c74214..ed584f9 100644
--- a/configure.in
+++ b/configure.in
@@ -358,7 +358,11 @@ case ${wal_segsize} in
  16) ;;
  32) ;;
  64) ;;
-  *) AC_MSG_ERROR([Invalid WAL segment size. Allowed values are 1,2,4,8,16,32,64.])
+ 128) ;;
+ 256) ;;
+ 512) ;;
+ 1024) ;;
+  *) AC_MSG_ERROR([Invalid WAL segment size. Allowed values are 1,2,4,8,16,32,64,128,256,512,1024.])
 esac
 AC_MSG_RESULT([${wal_segsize}MB])
 
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 39774a0..26bfab1 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -1049,7 +1049,7 @@ su - postgres
          the size of each individual file in the WAL log.  It may be useful
          to adjust this size to control the granularity of WAL log shipping.
          The default size is 16 megabytes.
-         The value must be a power of 2 between 1 and 64 (megabytes).
+         The value must be a power of 2 between 1 and 1024 (megabytes).
          Note that changing this value requires an initdb.
         </para>
        </listitem>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 58790e0..aa56a6b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -86,8 +86,8 @@ extern uint32 bootstrap_data_checksum_version;
 
 
 /* User-settable parameters */
-int			max_wal_size = 64;	/* 1 GB */
-int			min_wal_size = 5;	/* 80 MB */
+int			max_wal_size_mb = 1024;		/* 1 GB */
+int			min_wal_size_mb = 80;		/* 80 MB */
 int			wal_keep_segments = 0;
 int			XLOGbuffers = -1;
 int			XLogArchiveTimeout = 0;
@@ -738,6 +738,10 @@ static ControlFileData *ControlFile = NULL;
 #define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD)
 #define UsableBytesInSegment ((XLOG_SEG_SIZE / XLOG_BLCKSZ) * UsableBytesInPage - (SizeOfXLogLongPHD - SizeOfXLogShortPHD))
 
+/* Convert min_wal_size_mb and max wal_size_mb to equivalent segment count */
+#define ConvertToXSegs(x)	\
+	(x / (XLOG_SEG_SIZE / (1024 * 1024)))
+
 /*
  * Private, possibly out-of-date copy of shared LogwrtResult.
  * See discussion above.
@@ -2200,7 +2204,7 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, bool opportunistic)
 }
 
 /*
- * Calculate CheckPointSegments based on max_wal_size and
+ * Calculate CheckPointSegments based on max_wal_size_mb and
  * checkpoint_completion_target.
  */
 static void
@@ -2210,14 +2214,14 @@ CalculateCheckpointSegments(void)
 
 	/*-------
 	 * Calculate the distance at which to trigger a checkpoint, to avoid
-	 * exceeding max_wal_size. This is based on two assumptions:
+	 * exceeding max_wal_size_mb. This is based on two assumptions:
 	 *
 	 * a) we keep WAL for two checkpoint cycles, back to the "prev" checkpoint.
 	 * b) during checkpoint, we consume checkpoint_completion_target *
 	 *	  number of segments consumed between checkpoints.
 	 *-------
 	 */
-	target = (double) max_wal_size / (2.0 + CheckPointCompletionTarget);
+	target = (double) ConvertToXSegs(max_wal_size_mb) / (2.0 + CheckPointCompletionTarget);
 
 	/* round down */
 	CheckPointSegments = (int) target;
@@ -2229,7 +2233,7 @@ CalculateCheckpointSegments(void)
 void
 assign_max_wal_size(int newval, void *extra)
 {
-	max_wal_size = newval;
+	max_wal_size_mb = newval;
 	CalculateCheckpointSegments();
 }
 
@@ -2253,12 +2257,12 @@ XLOGfileslop(XLogRecPtr PriorRedoPtr)
 	XLogSegNo	recycleSegNo;
 
 	/*
-	 * Calculate the segment numbers that min_wal_size and max_wal_size
+	 * Calculate the segment numbers that min_wal_size_mb and max_wal_size_mb
 	 * correspond to. Always recycle enough segments to meet the minimum, and
 	 * remove enough segments to stay below the maximum.
 	 */
-	minSegNo = PriorRedoPtr / XLOG_SEG_SIZE + min_wal_size - 1;
-	maxSegNo = PriorRedoPtr / XLOG_SEG_SIZE + max_wal_size - 1;
+	minSegNo = PriorRedoPtr / XLOG_SEG_SIZE + ConvertToXSegs(min_wal_size_mb) - 1;
+	maxSegNo = PriorRedoPtr / XLOG_SEG_SIZE + ConvertToXSegs(max_wal_size_mb) - 1;
 
 	/*
 	 * Between those limits, recycle enough segments to get us through to the
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 291bf76..28e395c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -728,6 +728,11 @@ static const unit_conversion memory_unit_conversion_table[] =
 	{"MB", GUC_UNIT_KB, 1024},
 	{"kB", GUC_UNIT_KB, 1},
 
+	{"TB", GUC_UNIT_MB, 1024 * 1024},
+	{"GB", GUC_UNIT_MB, 1024},
+	{"MB", GUC_UNIT_MB, 1},
+	{"kB", GUC_UNIT_MB, -1024},
+
 	{"TB", GUC_UNIT_BLOCKS, (1024 * 1024 * 1024) / (BLCKSZ / 1024)},
 	{"GB", GUC_UNIT_BLOCKS, (1024 * 1024) / (BLCKSZ / 1024)},
 	{"MB", GUC_UNIT_BLOCKS, 1024 / (BLCKSZ / 1024)},
@@ -738,11 +743,6 @@ static const unit_conversion memory_unit_conversion_table[] =
 	{"MB", GUC_UNIT_XBLOCKS, 1024 / (XLOG_BLCKSZ / 1024)},
 	{"kB", GUC_UNIT_XBLOCKS, -(XLOG_BLCKSZ / 1024)},
 
-	{"TB", GUC_UNIT_XSEGS, (1024 * 1024 * 1024) / (XLOG_SEG_SIZE / 1024)},
-	{"GB", GUC_UNIT_XSEGS, (1024 * 1024) / (XLOG_SEG_SIZE / 1024)},
-	{"MB", GUC_UNIT_XSEGS, -(XLOG_SEG_SIZE / (1024 * 1024))},
-	{"kB", GUC_UNIT_XSEGS, -(XLOG_SEG_SIZE / 1024)},
-
 	{""}						/* end of table marker */
 };
 
@@ -2235,10 +2235,10 @@ static struct config_int ConfigureNamesInt[] =
 		{"min_wal_size", PGC_SIGHUP, WAL_CHECKPOINTS,
 			gettext_noop("Sets the minimum size to shrink the WAL to."),
 			NULL,
-			GUC_UNIT_XSEGS
+			GUC_UNIT_MB
 		},
-		&min_wal_size,
-		5, 2, INT_MAX,
+		&min_wal_size_mb,
+		5 * (XLOG_SEG_SIZE/ (1024 * 1024)), 2, MAX_KILOBYTES,
 		NULL, NULL, NULL
 	},
 
@@ -2246,10 +2246,10 @@ static struct config_int ConfigureNamesInt[] =
 		{"max_wal_size", PGC_SIGHUP, WAL_CHECKPOINTS,
 			gettext_noop("Sets the WAL size that triggers a checkpoint."),
 			NULL,
-			GUC_UNIT_XSEGS
+			GUC_UNIT_MB
 		},
-		&max_wal_size,
-		64, 2, INT_MAX,
+		&max_wal_size_mb,
+		64 * (XLOG_SEG_SIZE/ (1024 * 1024)), 2, MAX_KILOBYTES,
 		NULL, assign_max_wal_size, NULL
 	},
 
@@ -8078,6 +8078,9 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 			case GUC_UNIT_KB:
 				values[2] = "kB";
 				break;
+			case GUC_UNIT_MB:
+				values[2] = "MB";
+				break;
 			case GUC_UNIT_BLOCKS:
 				snprintf(buffer, sizeof(buffer), "%dkB", BLCKSZ / 1024);
 				values[2] = pstrdup(buffer);
@@ -8086,11 +8089,6 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 				snprintf(buffer, sizeof(buffer), "%dkB", XLOG_BLCKSZ / 1024);
 				values[2] = pstrdup(buffer);
 				break;
-			case GUC_UNIT_XSEGS:
-				snprintf(buffer, sizeof(buffer), "%dMB",
-						 XLOG_SEG_SIZE / (1024 * 1024));
-				values[2] = pstrdup(buffer);
-				break;
 			case GUC_UNIT_MS:
 				values[2] = "ms";
 				break;
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index d4abf94..d23aab5 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -94,8 +94,8 @@ extern PGDLLIMPORT XLogRecPtr XactLastCommitEnd;
 extern bool reachedConsistency;
 
 /* these variables are GUC parameters related to XLOG */
-extern int	min_wal_size;
-extern int	max_wal_size;
+extern int	min_wal_size_mb;
+extern int	max_wal_size_mb;
 extern int	wal_keep_segments;
 extern int	XLOGbuffers;
 extern int	XLogArchiveTimeout;
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 7dd3780..87d0741 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -218,7 +218,7 @@ typedef enum
 #define GUC_UNIT_KB				0x1000	/* value is in kilobytes */
 #define GUC_UNIT_BLOCKS			0x2000	/* value is in blocks */
 #define GUC_UNIT_XBLOCKS		0x3000	/* value is in xlog blocks */
-#define GUC_UNIT_XSEGS			0x4000	/* value is in xlog segments */
+#define GUC_UNIT_MB				0x4000	/* value is in megabytes */
 #define GUC_UNIT_MEMORY			0xF000	/* mask for size-related units */
 
 #define GUC_UNIT_MS			   0x10000	/* value is in milliseconds */