diff --git a/boa/environment.py b/boa/environment.py
index d0656274..fdc48186 100644
--- a/boa/environment.py
+++ b/boa/environment.py
@@ -329,5 +329,10 @@ def time_travel(
             assert blocks is not None  # mypy hint
             seconds = blocks * block_delta
 
-        self.evm.patch.timestamp += seconds
-        self.evm.patch.block_number += blocks
+        if (new_blknum := self.evm.patch.block_number + blocks) < 0:
+            raise ValueError(f"negative blocknumber: to set to {new_blknum}")
+        if (new_ts := self.evm.patch.timestamp + seconds) < 0:
+            raise ValueError(f"negative timestamp: to set to {new_ts}")
+
+        self.evm.patch.timestamp = new_ts
+        self.evm.patch.block_number = new_blknum
diff --git a/pyproject.toml b/pyproject.toml
index d7804fc1..a5ba2b5d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "titanoboa"
-version = "0.1.9"
+version = "0.1.10b1"
 description = "A Vyper interpreter"
 #authors = []
 license = { file = "LICENSE" }