diff --git a/git-p4.py b/git-p4.py
index ca6bb95c57..73f05f0a88 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -43,6 +43,9 @@ def __str__(self):
 # Only labels/tags matching this will be imported/exported
 defaultLabelRegexp = r'[a-zA-Z0-9_\-.]+$'
 
+# Grab changes in blocks of this many revisions, unless otherwise requested
+defaultBlockSize = 512
+
 def p4_build_cmd(cmd):
     """Build a suitable p4 command line.
 
@@ -249,6 +252,10 @@ def p4_reopen(type, f):
 def p4_move(src, dest):
     p4_system(["move", "-k", wildcard_encode(src), wildcard_encode(dest)])
 
+def p4_last_change():
+    results = p4CmdList(["changes", "-m", "1"])
+    return int(results[0]['change'])
+
 def p4_describe(change):
     """Make sure it returns a valid result by checking for
        the presence of field "time".  Return a dict of the
@@ -742,43 +749,77 @@ def createOrUpdateBranchesFromOrigin(localRefPrefix = "refs/remotes/p4/", silent
 def originP4BranchesExist():
         return gitBranchExists("origin") or gitBranchExists("origin/p4") or gitBranchExists("origin/p4/master")
 
-def p4ChangesForPaths(depotPaths, changeRange, block_size):
-    assert depotPaths
-    assert block_size
 
-    # Parse the change range into start and end
+def p4ParseNumericChangeRange(parts):
+    changeStart = int(parts[0][1:])
+    if parts[1] == '#head':
+        changeEnd = p4_last_change()
+    else:
+        changeEnd = int(parts[1])
+
+    return (changeStart, changeEnd)
+
+def chooseBlockSize(blockSize):
+    if blockSize:
+        return blockSize
+    else:
+        return defaultBlockSize
+
+def p4ChangesForPaths(depotPaths, changeRange, requestedBlockSize):
+    assert depotPaths
+
+    # Parse the change range into start and end. Try to find integer
+    # revision ranges as these can be broken up into blocks to avoid
+    # hitting server-side limits (maxrows, maxscanresults). But if
+    # that doesn't work, fall back to using the raw revision specifier
+    # strings, without using block mode.
+
     if changeRange is None or changeRange == '':
-        changeStart = '@1'
-        changeEnd = '#head'
+        changeStart = 1
+        changeEnd = p4_last_change()
+        block_size = chooseBlockSize(requestedBlockSize)
     else:
         parts = changeRange.split(',')
         assert len(parts) == 2
-        changeStart = parts[0]
-        changeEnd = parts[1]
+        try:
+            (changeStart, changeEnd) = p4ParseNumericChangeRange(parts)
+            block_size = chooseBlockSize(requestedBlockSize)
+        except:
+            changeStart = parts[0][1:]
+            changeEnd = parts[1]
+            if requestedBlockSize:
+                die("cannot use --changes-block-size with non-numeric revisions")
+            block_size = None
 
     # Accumulate change numbers in a dictionary to avoid duplicates
     changes = {}
 
     for p in depotPaths:
         # Retrieve changes a block at a time, to prevent running
-        # into a MaxScanRows error from the server.
-        start = changeStart
-        end = changeEnd
-        get_another_block = True
-        while get_another_block:
-            new_changes = []
+        # into a MaxResults/MaxScanRows error from the server.
+
+        while True:
             cmd = ['changes']
-            cmd += ['-m', str(block_size)]
-            cmd += ["%s...%s,%s" % (p, start, end)]
+
+            if block_size:
+                end = min(changeEnd, changeStart + block_size)
+                revisionRange = "%d,%d" % (changeStart, end)
+            else:
+                revisionRange = "%s,%s" % (changeStart, changeEnd)
+
+            cmd += ["%s...@%s" % (p, revisionRange)]
+
             for line in p4_read_pipe_lines(cmd):
                 changeNum = int(line.split(" ")[1])
-                new_changes.append(changeNum)
                 changes[changeNum] = True
-            if len(new_changes) == block_size:
-                get_another_block = True
-                end = '@' + str(min(new_changes))
-            else:
-                get_another_block = False
+
+            if not block_size:
+                break
+
+            if end >= changeEnd:
+                break
+
+            changeStart = end + 1
 
     changelist = changes.keys()
     changelist.sort()
@@ -1974,7 +2015,7 @@ def __init__(self):
         self.syncWithOrigin = True
         self.importIntoRemotes = True
         self.maxChanges = ""
-        self.changes_block_size = 500
+        self.changes_block_size = None
         self.keepRepoPath = False
         self.depotPaths = None
         self.p4BranchesInGit = []
diff --git a/t/t9818-git-p4-block.sh b/t/t9818-git-p4-block.sh
index aae1121b93..3b3ae1f59a 100755
--- a/t/t9818-git-p4-block.sh
+++ b/t/t9818-git-p4-block.sh
@@ -49,11 +49,11 @@ test_expect_success 'Default user cannot fetch changes' '
 	! p4 changes -m 1 //depot/...
 '
 
-test_expect_failure 'Clone the repo' '
+test_expect_success 'Clone the repo' '
 	git p4 clone --dest="$git" --changes-block-size=7 --verbose //depot/included@all
 '
 
-test_expect_failure 'All files are present' '
+test_expect_success 'All files are present' '
 	echo file.txt >expected &&
 	test_write_lines outer0.txt outer1.txt outer2.txt outer3.txt outer4.txt >>expected &&
 	test_write_lines outer5.txt >>expected &&
@@ -61,18 +61,18 @@ test_expect_failure 'All files are present' '
 	test_cmp expected current
 '
 
-test_expect_failure 'file.txt is correct' '
+test_expect_success 'file.txt is correct' '
 	echo 55 >expected &&
 	test_cmp expected "$git/file.txt"
 '
 
-test_expect_failure 'Correct number of commits' '
+test_expect_success 'Correct number of commits' '
 	(cd "$git" && git log --oneline) >log &&
 	wc -l log &&
 	test_line_count = 43 log
 '
 
-test_expect_failure 'Previous version of file.txt is correct' '
+test_expect_success 'Previous version of file.txt is correct' '
 	(cd "$git" && git checkout HEAD^^) &&
 	echo 53 >expected &&
 	test_cmp expected "$git/file.txt"
@@ -102,7 +102,7 @@ test_expect_success 'Add some more files' '
 
 # This should pick up the 10 new files in "included", but not be confused
 # by the additional files in "excluded"
-test_expect_failure 'Syncing files' '
+test_expect_success 'Syncing files' '
 	(
 		cd "$git" &&
 		git p4 sync --changes-block-size=7 &&