diff --git a/tests/test_tools.py b/tests/test_tools.py
index 6240143..d61e33b 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -133,7 +133,15 @@ def test_system_venv(self, tools_config):
         extra_pkgs = tools_config["environments"][test_target][
             "extra_packages"
         ]
-        extra_pkgs = " ".join(extra_pkgs)
+        pkgs_str = ""
+        ws = ""
+        for pkg in extra_pkgs:
+            pkgs_str += (
+                f"{ws}'{pkg}'"
+                if set(pkg).intersection(set("><"))
+                else f"{ws}{pkg}"
+            )
+            ws = " "
 
         expected = {
             "load": [f"source {self.lib_dir}/{test_target}/bin/activate"],
@@ -141,7 +149,7 @@ def test_system_venv(self, tools_config):
             "setup": [
                 f"rm -rf {self.lib_dir}/{test_target}",
                 f"python3 -m venv {self.lib_dir}/{test_target}  --system-site-packages",
-                f"pip install {extra_pkgs}",
+                f"pip install {pkgs_str}",
             ],
         }
 
@@ -272,7 +280,15 @@ def test_conda_pkgs(self, tools_config):
         extra_pkgs = tools_config["environments"][test_target][
             "extra_packages"
         ]
-        extra_pkgs = " ".join(extra_pkgs)
+        pkgs_str = ""
+        ws = ""
+        for pkg in extra_pkgs:
+            pkgs_str += (
+                f"{ws}'{pkg}'"
+                if set(pkg).intersection(set("><"))
+                else f"{ws}{pkg}"
+            )
+            ws = " "
         conda_cmd = tools_config["environments"][test_target]["conda_cmd"]
 
         expected = {
@@ -284,7 +300,7 @@ def test_conda_pkgs(self, tools_config):
             "unload": ["conda deactivate"],
             "setup": [
                 f"rm -rf {self.lib_dir}/{test_target}",
-                f"{conda_cmd} create -p {self.lib_dir}/{test_target} {extra_pkgs}",
+                f"{conda_cmd} create -p {self.lib_dir}/{test_target} {pkgs_str}",
             ],
         }
 
diff --git a/wellies/tools.py b/wellies/tools.py
index 768371a..9fe65dd 100644
--- a/wellies/tools.py
+++ b/wellies/tools.py
@@ -1,4 +1,5 @@
 import os
+import shlex
 from os import path
 from typing import Dict
 from typing import List
@@ -354,7 +355,7 @@ def __init__(
         ]
         if extra_packages:
             setup.extend(load)
-            pkgs = " ".join(extra_packages)
+            pkgs = " ".join([shlex.quote(pkg) for pkg in extra_packages])
             setup.append(f"pip install {pkgs}")
         super().__init__(name, depends, load, unload, setup, options=options)
 
@@ -544,7 +545,7 @@ def __init__(
             A dictionary of options for the tool, by default {}.
         """
         env_root = path.join(lib_dir, name)
-        packages_str = " ".join(packages)
+        packages_str = " ".join([shlex.quote(pkg) for pkg in packages])
         setup = pf.TemplateScript(
             conda_create,
             ENV_DIR=env_root,