diff --git a/version.go b/version.go
index 50d56b6..ea1aa1e 100644
--- a/version.go
+++ b/version.go
@@ -387,6 +387,9 @@ func (v Version) IncPreRelease() (Version, error) {
 	if !(v.IsPrerelease()) {
 		return Version{}, errors.New("version is not a prerelease")
 	}
+	if v.phaseSubOrdinal > 0 || v.customOrdinal > 0 {
+		return Version{}, errors.New("only unmodified CRDB versions are supported")
+	}
 	nextVersion := Version{
 		raw:          v.raw,
 		phase:        v.phase,
diff --git a/version_test.go b/version_test.go
index 7baa926..fb1dcba 100644
--- a/version_test.go
+++ b/version_test.go
@@ -704,10 +704,12 @@ func TestIncPreRelease(t *testing.T) {
 		{"v21.2.0-alpha.1", "v21.2.0-alpha.2", false},
 		{"v21.1.0-beta.3", "v21.1.0-beta.4", false},
 		{"v21.1.0-rc.3", "v21.1.0-rc.4", false},
+		{"v21.1.0-rc.3-cloudonly.1", "", true},
 		{"v21.1.0-cloudonly.1", "", true},
 		{"v21.1.0", "", true},
 		{"v21.1.8", "", true},
 		{"v26.4.8", "", true},
+		{"v26.4.8-cloudonly.1", "", true},
 		{"v21.1.0-customLabel", "", true},
 		{"v21.1.0-1-g9cbe7c5281", "", true},
 		{"v21.1.0-1-g9cbe7c5281-customLabel", "", true},