diff --git a/alibuild_helpers/utilities.py b/alibuild_helpers/utilities.py
index 4df262dc..a4b8912e 100644
--- a/alibuild_helpers/utilities.py
+++ b/alibuild_helpers/utilities.py
@@ -145,7 +145,16 @@ def resolve_version(spec, defaults, branch_basename, branch_stream):
   defaults_upper = defaults != "release" and "_" + defaults.upper().replace("-", "_") or ""
   commit_hash = spec.get("commit_hash", "hash_unknown")
   tag = str(spec.get("tag", "tag_unknown"))
-  return spec["version"] % {
+  version = spec["version"]
+  if not isinstance(version, str):
+    raise ValueError(
+      "Version for the package {package} must be a string, got {version}. "
+      "Please, make sure the version is quoted in the config file, e.g., \"1.0\"".format(
+        package=spec.get("package", "package_unknown"),
+        version=version
+      )
+    )
+  return version % {
     "commit_hash": commit_hash,
     "short_hash": commit_hash[0:10],
     "tag": tag,
diff --git a/tests/test_utilities.py b/tests/test_utilities.py
index f0cc2051..2a52aee6 100644
--- a/tests/test_utilities.py
+++ b/tests/test_utilities.py
@@ -400,6 +400,16 @@ def fake_abspath(n):
           self.assertEqual(resolveFilename({}, "zlib", "alidost"), (None, None))
           self.assertEqual(resolveFilename({}, "python", "alidist"), ("/bar/python.sh", "/bar"))
 
+      spec_float_version = {"package": "test-pkg",
+                            "version": 1.0,
+                            "tag": "foo/bar",
+                            "commit_hash": "000000000000000000000000000"
+                            }
+      self.assertRaises(
+        ValueError,
+        lambda: resolve_version(spec_float_version, "release", "stream/v1", "v1")
+      )
+
 
 class TestTopologicalSort(unittest.TestCase):
     """Check that various properties of topological sorting hold."""